CC Sabathia recorded 690 outs (230 ip * 3) and threw 3586 pitches. That equates to 5.2 pitches per out.
Mo Rivera, the closer, recorded 199 outs and needed 1028 pitches, for 5.17 per out.
Here's the full list:
Aceves - 4.96
Vazquez (in the lesser league) - 5.05
Rivera - 5.17
Sabathia - 5.20
AL avg. - 5.55
Burnett - 5.56
Pettitte - 5.59
Hughes - 5.64
Mitre - 5.65
Joba - 5.73
Gaudin - 5.80
Robertson - 6.62
The most interesting pitchers are at the top and bottom. 'Ace' doesn't seem like the most efficient pitcher on the Yankees, but he was last year, needing less than five pitches per out. Meanwhile, D-Rob, a very effective reliever, required almost seven pitches per out. (If he's going to evolve into a great reliever rather than just a good one, he'll need to cut down that number.) These are not the pitchers I would think of as the most and least efficient.
It's great that Vazquez had such a crazy low number (especially for a starter), but how will that carry over into the AL East in a homer-friendly stadium?
Hughes' pitches/out was a bit higher than I thought it would be. He seemed to mow down hitters with ease last year, yet he was still less efficient than starters like Burnett and Pettitte.