Jason Marquis has an impressive line this year. He’s 7-2, with a 3.53 ERA, and his BB/9 and K/BB are career bests as a full season starter. His K/9 is right on line with his career average. 
But that low walk rate has made everything else look better, including the Nats themselves. His FIP of 3.59 shows its not all smoke and mirrors, and that his ERA correctly reflects what he’s been doing. He has been very good this year, not just as an effective innings eater, but as a legitimate threat to win each time he goes out on the mound. And his BABIP of .303 is actually one of the highest in his career, suggested this isn’t just luck.
So can the Nationals expect him to do this from now on? Has he turned a corner in his career? Can they be confident that this pitcher will continue to throw the way he’s throwing? Unfortunately, probably not. It is rare for a pitcher to turn 32 and discover stuff that he never had before. Most of Marquis’ success, in fact, might not be totally attributable to a lack of walks. Instead, over his career, his ground ball percentage has been more highly correlated to his season ERA than those BB/9 or K/BB rates.
So he may not be doing much different with pitching, it’s just that the sinker is working well. And as you probably know, that is often based on “feel”. In other words, it could go at any minute. And there is no reason to think that next season, or the season after, he will keep his GB% above 53%, which is what he’s done this year, and his 2 other best full seasons, 2004 and 2009. The flexibility of his GB% over his career would lead one to believe that this isn’t a “new” Jason Marquis, or even the “real” Jason Marquis. It’s just another year of Jason Marquis. And if that GB% goes down to 49.5% next season, his ERA could very well jump to 4.60, which were numbers from his 2007 season.
The “So What” of Marquis
That isn’t to say it’s impossible that he’s changed, but the Jamie Moyer cases are far outweighted by everyone else in the league. After 12 seasons in the majors, about half of those as a full time/full season starter, he is the same guy he’s always been. That means that not only might he be a poor signing for next year, but he might not be great by the end of this year. If he loses that feel for the sinker, he may end up the season with a somewhat ok GB% (for him) around 51%. Which would mean, since the first half of the year he was at 53%, the second half he would sit at 49%. He he may supplement his first half ERA of 3.53 with a second half ERA of 4.75. By the end of the year, if you looked back and said “hey, Marquis pitched 200 innings and had a 4.30 ERA” (or whatever the numbers are), you’d be pretty happy. But in fact, that second half might be just as easily reproduced by a committee of youngsters from AAA.
I’m not saying that Marquis is guaranteed to regress THIS SEASON. But I think, because he hasn’t discovered a new pitch and is just pitching with an effective sinker, that he is the same guy he’s always been. Therefore, if someone offers them something of value in a trade for Marquis (who’s contract ends this season) they would be foolish to not take it. If you think Marquis is someone other than what he’s been all his career – a league average innings eater – you’re going to be disappointed in the future. There is value in that type of pitcher, but it isn’t something you hold onto when trade offers come in.
A Side Note/Link
The Riggleman situation stirred some historical feelings in Chris Jaffe over at Hardball Times. He wrote an article about other unusual managerial resignations over the years. Good stuff, if you’re into the history of the game.