With the signing of Jason Marquis, the free agent starting pitchers left on the board are all awfully similar in terms of likely value. If you like Doug Davis over Jon Garland, or Joel Pineiro over Davis, you're still not likely to get a frontline starting pitcher, and it is likely to cost a team roughly what Marquis cost the Nationals.
The two remaining starters with the chance to be much better than average- but carrying significant risk- are Ben Sheets and Pedro Martinez. With Martinez, we have a better sense of what he is looking for, contract-wise, thanks to ESPN.com's Jayson Stark reporting earlier today that he wants "more than Brad Penny got"- more than $7.5MM base salary, in other words. That's still in line with Marquis and company, however.
As for Sheets, he's reportedly seeking $12MM next year. So the question becomes, is Sheets likely to be more than a third better than Martinez?
The major advantages for Sheets: he's posted an ERA of 3.39 since 2007, while Martinez is actually below average during that time, at 4.66. Sheets has also made at least 30 starts as recently as 2008; Martinez last accomplished the feat in 2005.
But Martinez may be a better bet than that would suggest. For one thing, Sheets didn't pitch at all last season, while Martinez was quite effective- a 3.63 ERA in the regular season, 3.70 ERA in the playoffs. Martinez has also had a better strikeout rate than Sheets since 2007, which is a strong indicator of future performance.
If the price tag is significantly lower for Martinez- and as of right now, it appears to be- he might be the more valuable upside candidate of the two.
And if risk isn't your game, there's always Jon Garland.