It would seem like a good time for fifth starter discussion would be when pitchers and catchers report to camp. The alternatives today, though, would all entail complaining about Mark McGwire not getting in the Hall of Fame. Boring stuff, to be sure. So.....
Brad Hennessey
When he was moved to the bullpen last season, his velocity jumped by a couple of miles. That might have been a hot gun, or it might have been unrelated to the role change. Whatever the case, it can only reinforce the idea that Hennessey is destined for relief. He throws a good sinking fastball, an occassionally effective slider, and not much else. I have no idea why he's still considered a rotation candidate. He was much better last year as a reliever, and his profile has pointed toward relief since the day he was drafted.
Jonathan Sanchez
It's popular in some circles to break a young pitching prospect in with some indentured bullpen time, but I don't think a large-scale study has ever been done on the subject. Without any hard data, it doesn't seem right to point at Johan Santana and declare the strategy to be infalliable. The Giants could really, really use a hard-throwing, late-innings lefty for their bullpen, though. That would tempt me, and I while I'm rooting for Sanchez to win the rotation spot, he doesn't exactly have a full arsenal of pitches either.
Kevin Correia
Issues with iffy control can be minimized in the bullpen, and that's how Correia found some success last season. Like Sanchez and Hennessey, Correia has made a much better reliever in his short career than a starter.
Tim Lincecum
It messes up his service time (he'd be eligible for arbitration earlier) and it is goofy to jump young pitchers straight up from A-ball, but if Lincecum averages 15 strikeouts this spring would the Giants have a choice? There are plenty of other options, so they most certainly would have a choice. I'd rail against the decision, and be glued to every Lincecum start.
Russ Ortiz
It'd be perfect for Ortiz to come back to a team that he starred for; he'd have a great chance to be a league-average starter, and signing him would raise fan interest for sure. I'm just not sure that San Jose has room in their rotation.
The Jamey Wright Dark Horse Candidate Memorial Award winner if he signs, this idea would almost make sense in the right organization. If Sabean had any track record of trading overperforming veterans for something the team actually needs at the break, there might be some upside to taking a chance on Ortiz. But two pitching-starved franchises took a look at Ortiz, and wanted nothing to do with him this offseason -- one of those teams was the freaking Royals. A division rival had him on the roster, but preferred to pay him scores of millions to not pitch rather than pay him to pitch. His velocity is up in 15 winter league innings? Oh, sweet. You can file that with Lance Niekro's commitment to plate discipline last offseason.
Sun Woo Kim
Brian Cooper. That's a fun game. Let's try it again.
Sun Woo Kim
Brian Powell. One more time.
Sun Woo Kim
Jamey Wright. Okay, I'm done with the emergency eighth starter word association game. The problem is that the last guy actually won the job last season. There's no problem with having former prospects in AAA, though. And whenever I see a former prospect still struggling as a starter at age 28, I wonder if there would be a chance for him to increase velocity coming out of the bullpen. He isn't going to make an impact on the big club this year, so it's kind of a moot point.
To recap:
Will probably make better relievers in the long-term - Hennessey, Sanchez, Correia
Not quite ready, though a dominant spring could change that mindset- Lincecum
Whatever - Sun Woo Kim
"But then I thought, 'When am I ever going to be in Haiti again?'" - Russ Ortiz
Based on nothing but last year, I'd go with Sanchez, but it's early yet.