The biggest problem with last year's ballclub - really, every Yankee team since 2004 - was the starting pitchers' inability to get deep into games.
Length from the rotation is essential to keeping a team's bullpen fresh and effective, and also usually provides evidence that the starters are pitching well. You don't see a team leave its starters out on the mound if they're getting beaten up.
A.J. Burnett has thrown 64 innings in 10 starts, averaging 107 pitches per outing. His shortest start of the season thus far has been five innings. He's 3-2 with a 4.78 ERA, and the Yankees are 6-4 when he starts.
Pitching coach Dave Eiland apparently helped Burnett fix a mechanical flaw before his last start in Cleveland, and Burnett threw six shutout innings. I'd expect his numbers to get better as the season progresses.
Stalwart veteran Andy Pettitte has thrown 63.2 innings in 10 starts, averaging 105 pitches per start. He too has lasted at least five innings in every single game he's started.
His record is 5-1 with a 4.10 ERA, and the Yankees are 8-2 when he starts. He continues, year in and year out, to do exactly what the Yankees need him to do.
Most impressively, CC Sabathia has racked up a whopping 78 innings over 11 starts (7.14 IP per), averaging 110 pitches per start. Leaving out his disappointing performance on Opening Day (4.1 IP, 6 earned runs, 0 Ks), C.C. is 5-2 with a 2.93 ERA and is allowing only 1.03 baserunners per inning.
His strikeout numbers continue to be lower than his average (56 thus far in 78 IP), but as the weather heats up, he usually does too, so it's not a concern.
The performances of the Big Three are allowing youngsters Joba Chamberlain and Phil Hughes to work under less pressure, and making sure Girardi has a reasonably fresh group of arms in his bullpen from day to day.