Let's begin at the team level, then discuss individual men.
First, how much has luck affected results? Luck can work at two levels: games won from runs scored and allowed, and runs resulting from the on-field performance. On the games-won front, the Giants have had remarkably little effect either way. Calculating from actual runs scored and allowed, the team was perhaps 2 games under expectations; but figuring from calculated runs scored and allowed, which is a hair more accurate for reckoning future trends than actual runs, the team was almost perfectly on expectations. Then how about the runs themselves? Again, very little effect from luck: the runs scored are almost exactly correct to the run, and while the runs allowed are about 30 below calculations, most of that is probably from the Giants well-above-average defensive performance (second in the league to San Diego, whose extraordinary fielding helps explain their pitching performance). In short, luck--of either kind--is not much affecting the team's stats.
Next, still at the team level, we must ask how performance has compared to reasonable expectations. By "reasonable expectations", we will here use just projections from the players' career histories. (Note that those include 2010 data, so for players like Posey the "projections" essentially are their actual data.) For batting, the full (and current) pro-rated projections can be seen here, but the key points are these: first, the run-scoring value is virtually exactly as projected; second, the team line stats differ somewhat from projections in a systematic way ("systematic" in that the individual men's lines tend strongly to the same pattern), that being more walks with, of course, correspondingly fewer at-bats and so fewer hits and total bases, with the net just about balancing out as far as run-scoring goes. The key rate stats look like this:
Stat Actual Projected
Batting Average: .259 .265
Slugging Average: .400 .410
Walks (per PA): .081 .065
SOs (per PA): .170 .173
On-Base Average: .319 .313
Power Factor: 1.55 1.55
OPS: .719 .723
TOP Runs (to date): 344 346
I don't yet have comparably exact data for the pitching staff, but a rough estimate--based on hand-made calculations--is that the results are also very close to projections, within perhaps a few runs at most. So the long and the short of it is that at the team level, for the playing time allocated to the various men, the team's results are very, very close to what one would calculate based just on histories.
A note on projections from career histories: the traditional "sabermetric" estimate of peak-performance age has been 29; more recently, some have suggested ages as low as 26, but in my opinion the work by J. C. Bradbury of the Sabernomics site has pretty well verified that age. While the age/performance curve looks roughly parabolic, if we simplify with a linear approximation, and are willing to accept broad-brush generalities, the falloff for each year either side of the peak is perhaps 1% a year. A player who is 30 is thus at--in our approximation--typically at 99% of his peak; but his career data, assuming he came up at age 25, would indicate about 98%, so it actually, if slightly, under-represents his abilities. At age 31, he would be expected to be at 98%, while his career data would by then suggest the same value, so that he is well represented by those data. At 32, he is very slightly over-represented, 98% vs an actual 97%, and so on. But, while he is overstated once he is beyond 32, it is only by a very slight amount, because the running post-peak years bring the career totals down. In short, career-to-date stats are a pretty good indicator of true ability at almost any age.
Now let's look man by man, starting with the batters. For convenience, it's arranged by position, using the nominal occupant of that position.
1B: Aubrey Huff -- is thought to be having an amazingly over-expectations season. In actuality, the big change for him--as for many other Giants batters this year--is a significantly increased walks rate. In 332 PA, he had 10 walks over projection, which is a good bit (3% extra on the walks rate). Meanwhile, his hits and extra-base hits are very much in line with his prior work, though the 2 extra triples, artifacts of Park-of-many-Names, help the totals. But the shrinkage in at-bats makes the batting average--always a poor stat anyway--look artificially inflated for a roughly unchanged number of hits. Huff's overall numbers are very nice indeed, and their being rooted in career expectations save for the walks, which we hope are a result of BamBam's work, means that they may well be reasonably sustainable. With the Giants' best 1B prospect, Belt, being likely a full year away, it would behoove the team to re-sign Huff, even to a modestly multi-year deal, to bridge the gap to Belt, because Huff will probably have good trade value even by the time Belt is expected. (Incidentally, his BABIP is at exactly his career average.)
2B: Freddy Sanchez -- another man with substantially over-projections walks: an extra 6 in 179 PA, for an extra 3+% on his walks rate. But, at least at the mid-season point, his hits are down, and his overall offense value not really good. That is probably just chance (though his BABIP is almost exactly at career levels). At his career norms, FSanchez is a decent but not outstanding hitter for a middle infielder. Whether Brock Bond is a viable candidate for a starting major-league role is still much debated; he probably deserves a long look in 2011, because if he can't cut it, the Giants need to string FSanchez out as long as possible, which might be for as much as two or three years.
SS: Edgar Renteria -- for some reason, Renteria is an anti-favorite around here, and his current slump, even if brief, isn't helping convert anyone. Nonetheless, right now Renteria is an average defender at SS (the various fielding stats agree on that) and an above-average bat for a middle infielder, with 2010 stats very much in line with career projections right down the line. If Crawford, the heir apparent, is the goods, Renteria can be a bridge to him, and the Giants should exercise Renteria's 2011 option, but that's pretty much the limit. If Crawford is not the goods, the Giants have most of 2011 to find a successor to Renteria.
3B: Pablo Sandoval -- it is no secret that the Panda is performing far below expectations. Curiously, for all his flailing about, he was actually 2 walks over projections at mid-season, and correspondingly 2 strikeouts under; the bad news is not just that his power factor (TB/H) is down by a significant 6%, but that his formerly amazing BABIP--the core of his success in the past--has dropped from the .350 range to .287. The crux is whether that .350 (and .353 in 2008) was an illusion, however long-lasting, or whether he is just going through a phase now. There have to be some questions about his vision and the methods, which seem to vary by the day if not the inning, of correcting it (contacts, spectacles, goggles), which may have something to do with matters; and having his manager tell him, in nearly these words, "Screw plate discipline, just keep hacking" surely can't be helping matters. Basically, at least for the immediate future, as Panda's bat goes, so goes the Giants' offense. All we can do is wait and hope.
C: Buster Posey -- while he is everyone's darling, and clearly sound defensively (yes, Bruce, really he is), his offense right now is not what some seem to think. His walks rate iat the mid-point was an abysmal 3.5%, and his power factor that of a singles/doubles hitter (with the occasional long ball), not at all notable. His batting average was decent, but with a .324 BABIP. His overall net offense was decent, sound enough for a good catcher, but scarcely remarkable. None of that is to say much, based on 126 PAs not a few of which were not as a starter, about his long-term likely performance, but it would be wise not to think of him as the franchise bat, because--as many have noted--he is just not that kind of hitter: good for a catcher, yes, no doubt, but not Babe Posey.
LF: Pat Burrell -- he has clearly taken over as the regular LF for the team. At the mid-point, he was over-performing, but not, in count numbers, by very much: 5 extra hits (and with 3 fewer walks). Looking to his career stats as more indicative, he is a really good hitter, well more than enough to make up for his lack of speed (and he at least has ball sense and can usually catch what he can get to and--unlike some not so far away--usually has a good idea of where to throw the ball). If Thomas Neal can be ready in a year or thereabouts, Burrell is (like his friend Huff) a good candidate for a re-signing to act as a bridge to the prospect and still have decent trade value at that time. Right now, he, Huff, and Torres pretty nearly are the Giants offense.
CF: Andres Torres -- As I kept saying through much of last year (not to speak of the early part of this year), Torres is rather obviously the real goods, and is right now one of the three key pieces of the team's batting (aside from his fielding, about which little need be said). Installed in leadoff, he has jacked his walks rate, though at some cost to his power numbers (he can really drive a ball if he allows himself a "yucka-doo swing", which he does much less often this year). Right now, he is performing in overall worth at about 85% to 90% of last year's stats, which is about what one would expect, and is absolute gold for a CF with his glove skills. Fortunately, he seems a very young 32--"fortunately" because the Giants' best CF prospect (Peguero, if I believe what I read) is still dubious and in any event some ways away; the Giants need to re-sign Torres to something like a 3-year deal.
RF: Nate Schierholtz -- he is the RF more or less by default. This is clearly the Giants' biggest hole: even if Schierholtz could hit as he was doing during the stretch earlier this year when he was playing steadily, he would best be used as the rotating fourth outfielder. What is really wanted--nay, needed--here is the sort of bat that John Bowker's admirers think he could deliver. As things have fallen out, I reckon that even strong Bowker skeptics (including me) by now feel that he deserves one last, long look before the team gives up and makes a trade (unless something really advantageous, such as a Wheeler-for-X deal, with X a very big-bat/decent-glove 25-year-oldm turns up). Meanwhile, Schierholtz urgently needs more steady playing time if he is not to lose his skills for the rest of the season (and possibly get a possible career short-circuited).
Other Position Players:
Aaron Rowand: I've said it before, and I still say it--Rowand was never a terribly good bat, but there is something flat-out wrong with him. He is, in 237 PAs, off his norms by 7 hits and 5 walks, and that is how it's been since he got to San Francisco. But at this point, apparently neither he nor the organization has any idea what's wrong ("just a slump"), much less how to fix it, and he has turned into the second coming of Bengie Molina, a totally deadweight anchor on the team (who can't even catch the ball very well any more). For the good of the team, Rowand needs to get approximately zero plate appearances from here on out.
Juan Uribe: he is another one of those surprising walkin' fools: at the mid-point he was, in 306 PAs, a full dozen walks ahead of projection, an extra 4% on his walks rate, which is just jaw-dropping. As with Huff, it is the corresponding shrinkage in at-bats that makes his batting average look swollen, whereas in reality he was actually 3 hits under projections. It is his 5% jack in power factor that is probably the least sustainable part of his game (though it's actually not much above his 2009 PF). With his ability to play three IF positions somewhere from decently to well, Uribe's bat makes him both valuable and difficult to replace. Whether the Giants need to re-sign him--which may not be easy and will likely be expensive--depends in good part on whether DeRosa can be expected to be back at 100% of his former self for 2011; DeRosa can play SS well enough to take it once a week, which is all that is needed from the Uribe-type player, and he can play 3B and 2B well enough, too. Players with that versatility are extremely helpful, and one or the other of those two needs to be part of the team for a while to come. Considering ages and glove skills, I'd vote for re-upping Uribe for 2 or even 3 years.
Eli Whiteside: if the Giants would remember that Pablo Sandoval is a pretty good major-league catcher, and give him a couple of days a week behind the plate spelling Posey (who could play 1B one of those two days, spelling Huff), Whiteside could revert to his proper role, a defensive backup third catcher. Wee sprats may not recall this, but once upon a time still within living memory, almost evey team carried three catchers, knowing how draining the position is. With a Posey good for the years, and a Sandoval presumably good for the years (and for whom part-time catching would be a real help with his weight), the Giants have the luxury of double-backing-up the spot with a Whiteside, whose ability to work with Posey and Sandoval on defense would probably be a big plus.
Mark DeRosa: as noted above, especially valuable owing to his versatility. Overall career stats are decent but not outstanding, and he was probably mis-cast as a corner outfielder. If the Giants stick to their best men, it's hard to find a use for DeRosa despite his real value, and if he can prove his health in early 2011 he is probably best traded away. Or he could be kept as the emergency 3rd SS (after Renteria/Crawford and Uribe), though he's costly for that role--still, it's sunk costs.
Travis Ishikawa: not a major-league corner bat. As to the value of a weak-bat/good-glove 1B, ask Skip James.
No one else who has played or might play this year seems worth comment.
Turning to pitching (here, we will be a little less quantitative and more qualitative, but there are numbers underlying the ideas):
Assuming that Bumgarner is now solidly welded into the rotation, it looks awfully strong. So far, Lincecum's numbers are down a bit from projections (and, we hope, just in a flukey manner), but Cain's are up by a little more, and that about evens out; JSanchez is, unsurprisingly, far ahead of projections, but we all hope that that is sustainable owing to his having turned the proverbial corner in his career.
The bullpen has been made to seem shakier than it is by a combination of two things: some guys each going through a fairly brief bad spell and several guys who absolutely, positively should never have been there. If we pull out the best performers, looking for a 7-man pen, we easily get (alphabetically): Affeldt, Martinez, Mota, Ray, Romo, Runzler, and Wilson. What that means is none of Bautista, Casilla, Joaquin (at least for now), Medders (once and possibly still useful, but now superseded by the younger and probably better Martinez), and--of course--Wellemeyer (what were they dreaming of?). A few words about the pen lads (again alphabetically):
Jeremy Affeldt: he had a rough stretch, possibly augmented by physical issues, but, while wildly unlikely to ever again repeat his 2009, he remains a better-than-average, quite useful part of the pen. Affeldt has the pleasant distinction of being almost equally effective against RHB and LHB.
Joe Martinez: he has yet to look good at the major-league level, but there were excellent reasons in later 2009, and so far this season a .333 BABIP hasn't helped him. He is likely not a real 5th starter, but should be a good long-innings pen man.
Guillermo Mota: he has a striking--nearly amazing--career BABIP of only .272, and that's over a long career (over 3,000 batters faced). He's never Hall of Fame, and occasionally gives up XBH, but he has decent walks and strikeouts rates (career K/W over 2.4) and a career OBP yielded under .300 (.291). In short, he is an unspectacular but notably better than average reliever. At his age, he is not a long-term asset, but he takes pressure off any need to rush a replacement.
Chris Ray: as he is still nominally in recovery from Tommy John surgery, we need to be carful evaluating him--his post-op 2009 is meaningless, and we need to essentially clear the slate. So far in 2010, his results are good, but there are flags up: a K/W barely over 1, and a TB/H ratio somewhat above league norms. But his pre-op history is that of a good pitcher, so one supposes that "guarded optimism" is the order of the day.
Sergio Romo: an excellent pitcher whose remarkable slider will, every once in a while, hang, leading to slightly more homers than normally expected. All in all, though, an obvious setup man with a very possible closer's role in his future.
Dan Runzler: His meteoric 2009 was an act anyone would find hard to follow, including he himself. But after an adjustment period earlier in the year, he looks on track for being a solid later-inning guy. Regrettably, his platoon splits are rather sharp, so he is probably limited in use against RHB.
Brian Wilson: he can be heart-attack-inducing, and his overall numbers, while good, do not leap off the page and grab one by the throat. He seems to eventually get the job done, but it may be worth recalling that he blew 6 saves in 2008 and 7 in 2009, and has a career saves/opportunities rate of about 86%, pretty good but not superlative. But there seems no need to be looking for a replacement yet.
As many writers have pointed out, saves and "closers" are somewhat artificial creations; the average pitcher throws 70% scoreless innings, and in save opportunities there is often a 2- or even 3-run lead, so that a perfectly scoreless inning is not needed for the save. One doesn't have too be so very good to get a high saves percentage if used in save situations. That doesn't mean that high-percentage closers are not pretty good pitchers, only that save percentages don't well measure much about quality.
Denny Bautista: an open gas can.
Santiago Castilla: also do not smoke in his vicinity.
Brandon Medders: a somewhat but not exceptionally better than average long-innings guy whose day is now past for the Giants in that they seem to have better and younger men who can fill the role.
Todd Wellemeyer: probably nice to children, dogs, and little old ladies, and as a pitcher worth what that sort of behavior is worth.
Waldis Joaquin: I know little save that he is not ready for prime time. Maybe he's in line for Mota's spot in 2011; maybe not.
In sum: this team has enough solid talent in both pitching and offense to be a serious contender, in 2010 and beyond, but only if--and I mean only if--the management at both the field level and in the front office recognizes who's valuable and who isn't and uses the men accordingly. (I will spare you all yet another repetition of my suggested 10-man position-player rotation, but as Casey said, "You could look it up.") So far this year, on offense alone the Giants have given from one-quarter to one-third of their plate appearances to men who should never have gotten any. That's like playing 75 games, 50 games with your good major-league team and 25 with a mediocre triple-A team--how much do you expect to score?