Derek Lowe is the best remaining free agent starting pitcher. Many people still debate whether Oliver Perez or Derek Lowe should be the Mets main target, but there's no contest. Oliver Perez had one season (2004) that compares with what Derek Lowe has been basically doing his entire career. Ollie does have age in his favor, but Lowe's skills (sinker/groundballs) actually age much better than Perez's (strikeouts).

Instead I want to weigh Perez against another, less-mentioned free agent starter, Ben Sheets. Since Sheets doesn't have a Scott Boras packet comparing him to Sandy Koufax, I'll have to make the case for him.

Projecting 2009

Bill James Projections clearly favors Sheets. Even with a projected gap of about 20 innings in Perez's favor, Sheets is 12 million dollars more valuable. Assuming each pitcher signs for something between 12-16MM a year, this deficit could represent the difference between the Mets getting a positive or negative return on their investment. Some projection systems are more forgiving to Perez, but all rate a relatively healthy Sheets better than Perez by a wide margin.

Health

Sheet's health, however, is no guarantee. Here's his DL History (hat tip, River Ave. Blues):

Aug 14, 2001 - Sept 21, 2001: rotator cuff tendinitis
April 25, 2005 - May 27, 2005: viral & ear infection
Aug 27, 2005: torn lat muscle (out for remainder of season)
Mar 30, 2006 - April 16, 2006: right shoulder strain
May 10, 2006 - July 24, 2006: right shoulder tendinitis
July 17, 2007 - Aug 29, 2007: sprained middle finger on throwing hand

After having a season for the ages in 2004, Sheets has yet to complete a "full" 200 inning season. His only real injury concern going forward, however, is his pitching shoulder problems from 2006. The other three listed injuries, an ear infection, a sprained finger, and a lat tear, do not figure to be recurring. Late last year Sheets suffered a torn muscle in that same right shoulder, which he characterized as only "short term." Although his shoulder remains a red flag going forward, a case could be made that Sheets has been more unlucky than "injury prone."

Perez has had injury problems of his own, most notably a lower back injury around the All-Star Break in 2007. In fact, Perez has never pitched 200 innings in a season, whereas Sheets has achieved the feat three times. Minor league demotions and reduced roles have been more the undoing of Perez than injuries, but that fact should only underscore the gap in talent between these two pitchers.

Stuff/"Potential"

The chief argument for Ollie is that he maintains "ace potential" based on his high strikeout rates. If only he could cut down on his walks, he'd be the kind of pitcher Scott Boras pretends he is. This transformation would be no small feat, however, as Perez lead of all of baseball in walks last year and isn't exactly learning to pitch. Although 27 is relatively young, it's not developing-my-mechanics young, and we may have already witness Oliver's prime.

Another problem with this idea is whether Perez's approach would even allow it. Take a look at his two pitches (fastball, slider) in 2008 through Pitch f/x:

Perez is notorious for slinging the ball at the plate without consistent result. The various positions of his slider on the graph above reflects this approach.Too make matters worse, Oliver nearly always throws a fastball down in the count. Last year he threw 32/32 fastballs down 3-0. While this isn't a terrible idea, his inability to keep the fastball down in the zone leads to several home runs and walks.

Calls for Oliver Perez to simply stop walking people is like asking Russel Branyan to stop striking out so often. If Branyan didn't swing like he was golfing, he wouldn't be hitting homeruns in the first place. If Perez didn't challenge hitters with high fastballs or throw his inconsistent slider early in the count, he wouldn't get the same high number of strikeouts. Perhaps with his fantastic stuff, Perez could employ a better approach successfully, it just doesn't seem likely at this point.

Even in his mythical 2004 season, Perez posted just a 2.95 K/BB, well below Sheet's career 3.85 mark. Not to mention Sheets posted a ridiculous 8.25 K/BB that same 2004 season with 264 strikeouts to just 32 walks.

Defining Replacement

If you're still worried about Sheets' injury history, then consider the possible ramifications of him missing time. Assuming the Mets get Derek Lowe (or another lesser starter) the rotation would be Santana-Lowe-Pelfrey-Sheets-Maine leaving Jonathon Niese out of the equation. If Sheets misses any amount of time, Niese represents a replacement many project to be better than Perez in 2008. There should be serious practical concerns when choosing between two players the spot starter sits between on the talent spectrum.

Conclusion

So you want a starter who is relatively young, has show flashes of dominance in the recent past, and has ace upside at third starter price? Take Sheets; the upside is greater and the risk is smaller than you think.