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July 20, 2007

Prospectus Today

Upstairs Downstairs Out West

by Joe Sheehan

Strange doings in the American League West...

Team      Record   Pct     RS   RA
Seattle   53-39   .576    456  445
Oakland   45-50   .474    402  391

The Mariners and A’s have the exact same run differential, +11, and yet are separated by nine-and-a-half games in the standings. The Mariners are a contender—two games out in the AL West, and 1 ½ out in the wild-card chase—while the A’s are going to play out the string without much hope of a postseason berth for the first time since 1998.

Statheads look at run differential—as opposed to wins and losses—as a measure of team quality because teams don’t have the ability to distribute their runs in a manner that causes them to win more often than those two basic measures suggest they should. In any given season, some teams outperform or underperform their record, but those variations have never been shown to be the result of an ability or inability to score timely runs. Bullpens have been shown to have an effect, with good ones enabling a team to win more close games and thus get an edge on their RS/RA. There’s some belief that a manager’s choice of tactics and personnel in lost causes can skew the numbers, with some teams more prone to turning big losses into bigger ones, which would affect the RS/RA.

In the specific case of the 2007 Mariners, it appears that their record diverges from their RS/RA for two specific reasons: they have the best bullpen in baseball so far, and they’ve lost some games by a lot of runs. The Mariners are 16-11 in one-run games, 22-14 in one- and two-run games, and over .500 at every stop until you get to five-run games (4-7). At the other end of the spectrum, though, the Mariners have lost five games by at least nine runs, and are 0-5 in games decided by more than eight runs, a deficit of 58 runs in blowouts. (They are, oddly, 5-0 in games decided by exactly eight runs, which makes up most of the gap.) As the bullpen has driven the close-games record, the rotation—due to an unhappy number of disaster starts from Jeff Weaver, Ryan Feierabend, and Horacio Ramirez—has been responsible for those big losses.

You can see, though, that we’re not necessarily talking about “luck” here. The Mariners’ record in close games and blowouts is tied to their personnel, or at least its performance to date. Whether they can continue to play .576 ball with a .510 run differential is most likely tied to whether their bullpen, which has been insanely great—fourth in WXRL and Adjusted Runs Prevented, led by two guys who’ve posted an ERA of 0.97 in 74 1/3 innings—can continue to perform at this level. There’s enough disconnect between the peripherals and the ERAs of Brandon Morrow and Eric O’Flaherty to project some slippage over the next ten weeks. One key statistic to watch: the top five relievers in the Mariners’ pen have allowed seven homers, total, this season. That number is almost certain to rise.