Yankees 2009 Starting Rotation

So far this off-season the Yankees have added CC Sabathia and AJ Burnett but they have also lost Mike Mussina to retirement and Andy Pettitte is a free agent who may not be returning. So in essence you have added two starting pitchers and have probably lost 2 starting pitchers. How do the pairs compare? Using 2008 numbers:

Sabathia 17-10 / 35 GS / 253 IP / 76 ER / 2.70 ERA
Burnett 18-10 / 35 GS / 221 IP / 100 ER / 4.07 ERA
Combined 35-20 / 70 GS / 474 IP / 3.34 ERA / 6.77 IP/GS

Mussina 20-9 / 34 GS / 200 IP / 75 ER / 3.37 ERA
Pettitte 14-14 / 33 GS / 204 IP / 103 ER / 4.54 ERA
Combined 34-23 / 67 GS / 404 IP / 3.97 ERA / 6 IP/GS

The incoming tandem had 1 more win and 3 fewer losses (and yes I know how subjective wins and losses are). Even if you added 4 additional wins to the Yankees in 2008 - they still would have finished in 3rd place.

Probably most significant among the above stats is the fact that the new combo pitched about 1 more inning per start than the old combo. The Yankees bullpen was a weak spot for the team last year (and probably next as well) so going deeper into a start is a big plus. The caveat that has to be noted is that both CC Sabathia and AJ Burnett had their career bests in innings pitched last year. Asking them to match those numbers may be asking too much. It is very likely that the extra inning per start will evaporate and the production levels will be along the lines of what Mussina and Pettitte contributed.

An independent measurement of a player's contributions is Bill James' Win Share Method (where 4 win shares = one team win). Here's how the 4 players did in 2008:

Sabathia 25 WS
Mussina 18 WS
Burnett 14 WS
Pettitte 11 WS

Based upon those numbers the incoming duo had 10 more win shares which translates to 2.5 more wins. Which again wouldn't have been enough to have gotten the Yankees out of 3rd place last season.

I guess this is a long way to explain that Yankee fans shouldn't be placing orders for World Series travel plans quite yet.