How will Rocket's return impact AL East race?

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	Roger Clemens dominated NL batters for the past three seasons, but now he heads back to the rough and tough AL East. Bob Rosato/SI

By Joe Sheehan, BaseballProspectus.com

With a dramatic seventh-inning announcement, Roger Clemens made himself a returning hero, a difference-maker, and a whole big pile of cash.

Clemens, who was on his way into retirement the last time he was being cheered wildly by a Yankee Stadium crowd, agreed to a one-year, $28-million contract to don pinstripes for the remainder of 2007. The deal is the biggest in baseball history by average annual value, and includes the highest single-season salary ever paid to a major-league player. Clemens won't get quite that much money, as he won't join the Yankees for another month, but two-thirds of that figure, about $18.5 million, makes for quite the incentive to return. The cost is greater to the Yankees; throw in the luxury tax hit on this addition to the payroll, and they're committing about $26 million.

It's not for "four months," however, as has been reported -- the Yankees don't make a signing like this without expecting to get an extra month from the player. Signing Clemens addresses the Yankees' biggest problem to date, a starting rotation that has left it behind the eight-ball -- or eight-spot -- in far too many games. It provides an upgrade from Kei Igawa, who looks overmatched, to a legitimate No. 2 starter, while also preventing Clemens from providing a comparable upgrade to the Red Sox, who were spurned in the bidding for their former ace.

What kind of impact are we looking at here? Remember that due to injuries, the Yankees have gotten a lot of starts from pitchers who weren't part of their master plan in February. Chien-Ming Wang and Mike Mussina are back, Andy Pettitte never really left. Darrell Rasner pitched well enough yesterday, especially on the heels of Igawa's stinkbomb on Friday, to argue for a spot ahead of the Japanese left-hander. Philip Hughes is expected to return a bit after Clemens does. So let's say that Clemens will be replacing Igawa, while Hughes takes Rasner's spot.

Nate Silver's PECOTA system projects Clemens, conveniently, for 21 starts, maybe one or two shy of what he'll make for the Yankees. The system has Clemens posting a 3.34 ERA in a neutral environment, worth 28.3 runs over replacement, and 3.6 wins above replacement. None of that seems out of line; it would make Clemens one of the ten best starters in the AL on a per-inning basis. I can see an argument that the projection is slightly optimistic because Clemens' most recent work was in the NL, and he'd be pitching for an AL East team, but remember that both PECOTA and the Translations system are accounting for that.

PECOTA projected Igawa to post a translated 4.28 ERA in 180 innings, worth 22.9 points of VORP and 4.1 WARP. However, we have additional information on Igawa, his first 30 or so major-league innings, which indicate that those figures are high. Igawa has allowed eight home runs in 30 2/3 innings, leading to a 7.63 ERA. His translated ERA is 7.45, with negative VORP (-11.5) and WARP (-0.7) totals. If you weight the projection and the performance to date, allowing the latter to make up 1/6th of the line, you should get a more accurate projection.