This is the type of game that the Yankees gave CC Sabathia $161 million for: To stop a losing streak against our arch-rival to put us into a first place tie.
Sabathia's been by far our best and most consistent starter. He hasn't faced Boston since 2007, when he made three starts (once in the regular season, and twice in the playoffs), allowing 13 runs in 17.1 ip. After a rough first six games, Sabathia's turned it on in his last six: 47 ip, 2.49 ERA, 37 K, .91 WHIP.
On the other side, Brad Penny has been Boston's (second) worst starter, but you pretty much know what you'll get from him: About six innings and two to five runs allowed (he's gone between 5.1 and 6.2 innings in all but two games this season, and has allowed between two and five runs in all but one game). He hasn't faced the Yanks since the 2003 World Series.