On paper, the Yankees have one of the best rotations in baseball, perhaps the best if you feel optimistic and are willing to gift them with 30 starts apiece from A.J. Burnett and Joba Chamberlain.

Burnett has No. 1 starter stuff -- sitting in the mid-90s with a hammer curve, a plus changeup he should use more, and a cutter he just started using in the last year or so to give hitters another thing to worry about. He has no major weaknesses on the mound. He's not prone to the long ball, not too wild, he gets hitters on both sides of the plate out and he misses a ton of bats. That last point is particularly important for a pitcher going to the Yankees, who look like they're going to have a below-average defensive club, and perhaps a bad one, depending on what they do in center field and how much more rope they're willing to extend to second baseman Robinson Cano. He can be prone to the One Bad Inning, but he's not in Javy Vazquez territory.

There are two major drawbacks to a Burnett signing of more than one year. One is that he doesn't always pitch up to his stuff; last year, he had a 4.96 ERA at the All-Star break, and over three years with Toronto he didn't post a single-season ERA under 3.75. Yet he finished his three years in Toronto on a tear, with a 2.72 ERA, 105 strikeouts against 29 walks in 94 1/3 innings, and dominant outings against the Yankees (four starts, 32 1/3 innings, five earned runs), Rays (two starts) and White Sox (one start) after the 2008 All-Star break. If he pitches like that over a full season, he will be a Cy Young contender. But he hasn't pitched like that over a full season at any point in his career, and he has only pitched like that in years when he had a significant financial incentive to do so (his walk years and his last pre-arbitration year).

The other is the frequency with which he takes the mound. Burnett has, with some reason, earned a reputation as a pitcher who will only pitch if his arm feels 100 percent, even though most pitchers pitch from time to time with some soreness or mild discomfort. Burnett has had only one serious arm injury in his pro career -- the blown elbow ligament that cost him most of the 2003 season -- but has missed time with "minor" arm problems that never required surgery. As a result, he has thrown only 200 innings in a season three times (the aforementioned years when there was money at stake), and has only made 30 starts in a season twice. An optimistic forecast would only give him 125 or so starts across the five years of this contract with the Yankees.

I've seen Burnett compared to Carl Pavano by fans, but the comparison doesn't hold. Pavano was more injury-prone at the time he signed with the Yankees than Burnett has been; Pavano had shoulder or elbow trouble in just about every season of his career until he rattled off two straight healthy years with Florida. Pavano also had nowhere near Burnett's raw stuff, nor his ability to induce strikeouts or ground balls. It is, of course, possible that Burnett's tenure with the Yankees will resemble Pavano's; pitchers do get hurt, and Burnett has some affinity for the trainer's room. But Burnett brings an upside to the table that Pavano never did: that of a shutdown No. 1 starter who, in the Yankees' rotation, will always be pitching in the spot of a No. 2 or 3 starter.