C.C. Sabathia 2008 Pitching Splits - Baseball-Reference PI
Vs. Cubs: 3 GS, 1-1, 22.2 IP, 2.78 ERA
Vs. LAD: 1 GS, 7 IP, 1 ER
Vs. HOU: 1 GS, Win, 9 IP, 2 ER
Vs. STL: 1 GS, Win, 9 IP, Shutout
And two of the three Cubs games came after mid-September.
He has a career 2.77 ERA in September and October (regular season), almost a half-run better than any other month.
If you want to talk playoff stats, you have to bring up that he only has five total playoff starts in his career, including this season. And you can't ignore that he started four straight times on three days' rest this season (before only getting one playoff start, which goes back to the above mention of the sample size).
Maybe he should go to a team that knows how to build a pitching staff where they don't have to ride one or two pitchers all the way down the stretch.