That is a very interesting question by colleague David Schoenfield. Andy Pettitte turns 40 this season so here are some of Schoenfield's findings of pitchers who were 40.
Fifteen of the 19 posted an ERA+ of league average or better. This makes sense; only good pitchers are still around at age 40 and old pitchers are going to be on a short leash if they're not any good. So if an old pitcher remains in the rotation it's because he's at least decent. I suspect this would be the case with Pettitte; he's either the same as he's always been or gets shelled over a few starts and hangs 'em up again.
Collectively, the 19 pitchers posted a 3.76 ERA at age 40 ... and a 3.85 ERA at 38. They actually pitched more innings at age 40 -- 3788.1 to 3540.2. Of course, none of them missed an entire season at age 39. Again, this would seem to confirm the above statement: If Pettitte remains reasonably healthy, he should be the old Andy Pettitte.
Eleven of the 19 had a better ERA+ at age 40 than age 38, although the margins were very close in some cases. The only pitcher with a significant drop from his age-38 ERA to age 40 was Orlando Hernandez, who posted a 3.30 ERA in 15 starts with the Yankees in 2004 but a 4.66 ERA in 29 starts with the Diamondbacks and Mets in 2006.
Here is the link to read the whole post.
QUESTION: Will Pettitte be the same as his All-Star 2010?