How Might Losing Buster Posey Affect the Giants?

Whenever I see an injury occur-baseball or otherwise-I cringe, and I immediately think, "wow, that sucks."  There's always a bit of a detachment involved, simply because there isn't any real connection to the individual.  Watching Buster Posey get hit the other night, though...wow.  Some of what I felt could be expressed in clichés-my stomach dropped, my heart sank, and so on-but at the bottom of it all was this overwhelming feeling of despair.  I just witnessed a spectacular ballplayer and a fantastic young man writhe in pain after a collision gone wrong.

 Buster was an integral part of the Giants' surge last year that brought a World Series title to San Francisco, and he is a key piece of the Giants' lineup.  True, he wasn't lighting the world on fire-he was hitting .284/.368/.389 with nice on-base skills but little power-but that's darn good for a catcher, and he was one of the few hitters that has produced for the Giants above the league average rate, with potential for more.  ZiPS Rest of Season (ROS) projections forecasted him to finish the year with a .293/.368/.443 line, +22 runs above average.  That's an extremely valuable player, especially behind the plate, and...he's gone.

 As of right now, the Giants have two catchers on the roster in Posey's absence.  The first is Eli Whiteside; the second, Chris Stewart.  Both players are essentially backup receivers, with Whiteside a career .231/.283/.366 hitter and Stewart a .188/.235/.229 hitter in 54 PA at the Major League level and with little success in the Minors.  We know that the Giants have suffered an incredible loss offensively-the question is, how much have they lost?

The simple approach would be to use the player's ZiPS ROS, find their estimated value and then to look at the difference.  This approach suggests that the difference between Buster and Eli-between 453 plate appearances-is close to 30 runs.  This, of course, does not account for playing time given to Chris Stewart, or to another catcher should the Giants acquire one (rumor has it they've already asked about Ivan Rodriguez).  Nor does it adjust for the plate appearances Eli wouldn't take-remember, he would be hitting in the lower part of the order, where he will receive fewer plate appearances per game-so it's a bit hard to tell.  In any case, we're looking at about three and a half wins lost (generally speaking, ten runs equals a win-but for the Giants, who play in a lower run environment, it's about nine runs).

Another way to estimate the impact of Posey's bat within the Giants lineup is to use a Markov Chain, which is a mathematical model that uses transition probabilities to move from one state to another.  Since baseball is a game of states (nobody on, runner on first no outs, runner on first one out, etc.), Markovs work exceptionally well for lineup analysis.*  For example, this is the most common lineup (given the return of Andres Torres and the loss of Pablo Sandoval):

 

  1. Andres Torres
  2. Freddy Sanchez
  3. Aubrey Huff
  4. Buster Posey
  5. Nate Schierholtz
  6. Cody Ross
  7. Mike Fontenot
  8. Miguel Tejada
  9. Pitcher

 

Using up-to-date stats, this lineup would be expected to score 3.83 runs per game according to the Markov.  The Giants have actually scored 3.54 runs per game, which can in part be explained by Bruce Bochy's different daily lineups and the fact that Aaron Rowand led off a lot.  Substituting Rowand for Torres drops the Markov estimate to 3.53 runs per game, so it works reasonably well at capturing reality.

 With the return of Brandon Belt, Pablo Sandoval, and some overall regression to the mean, the Giants should see a definite increase in their offensive output.  I figure this is a reasonable estimate of how the normal lineup would play over the course of the season, assuming Buster never suffered his injury:

  1. Andres Torres
  2. Freddy Sanchez
  3. Aubrey Huff
  4. Buster Posey
  5. Pablo Sandoval
  6. Cody Ross
  7. Brandon Belt
  8. Miguel Tejada
  9. Pitcher

This lineup is expected to score 4.82 runs per game.  I know the figure seems a bit high, and it is-but bear with me.  It's more important to pay attention to the difference than anything else.  If we were to subtract Posey, shift everyone down a slot and hit Eli Whiteside eighth, that expected runs per game figure changes to 4.54.  Over the remaining 112 games, this would amount to (4.82 - 4.54) x 112 = 31 runs, right in line with the simple estimate.

 So, the bottom line is that we're looking at about three wins lost with the absence of Posey.  If the Giants are a true .564 team and they're playing .551 ball, they would be expected to finish the season with a .557 winning percentage and 90 wins.  By losing Buster, this drops their expected wins to 86.  By the same estimates, the Rockies are a true talent .525 team currently playing .490-so they look to wind up somewhere around .511 and 83 wins-only three games behind.  That's a pretty small gap, so the Giants need to either A) acquire some help, B) hope their players either match or exceed their ROS forecasts, or C) hope the rest of the NL West performs poorly to help compensate for the loss of Buster.  As it currently stands, it looks like we'll be biting our nails rather than being relatively comfortable towards the end of the season.

Get well soon, Buster.  We need you.

 

*A popular lineup tool on the internet is the Baseball Musings tool, which only uses on-base percentage and slugging percentage.  I prefer the Markov approach because it follows the rules of baseball, whereas the Musings tool is based purely on regressions and doesn't actually take into consideration the interactions between players.

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