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The John Dewan Rule
Posted By Bill Baer On March 23, 2011 @ 10:03 am In MLB,Philadelphia Phillies,Sabermetrics | 15 Comments
Ask any Saberist what they think about spring training, and you are likely to get the same answer across the board: “It’s meaningless.” And they’re right, almost entirely. Spring training really is a breeding ground for bad analysis for a multitude of reasons, most importantly the small sample sizes. Jimmy Rollins is currently the Phillies’ leader with 59 at-bats. As Eric Seidman listed here, the only two stats that become reliable between 50 and 100 trips to the plate are swing and contact rates.
When you break Rollins’ 59 AB down further, you find that he is not exactly facing premier Major League talent through and through. He is facing #5 starters vying for a job, middle-rotation guys working on a new pitch, and even Triple-A filler*. Sure, he faces the Jon Lesters of the world too, but those at-bats are not the overwhelming majority. Hitters are always tweaking things as well, such as the openness of their stance, their proximity to home plate, or the height of their hands prior to a swing a la Domonic Brown.
* Also known as the Yankees’ #3 starter. Boom! Roasted!
There is, however, one way to use spring training stats to get a general feel of the upcoming season. John Dewan was one of the few to foresee the breakout of Jose Bautista, who went from a previous career high 16 home runs to 54 last year.
How did he do it? By comparing hitters’ spring training slugging percentages to their career average slugging percentage. If the difference is 200 points or greater in favor of spring training, then the hitter has a 60 percent chance of a breakout season.
Here are the leaders in slugging percentage among Phillies with 35 or more AB this spring:
According to this theory, both Orr and Valdez are primed for breakout years, with Francisco on the cusp. Maybe the Phillies didn’t need Luis Castillo after all.
Obviously, apply extreme skepticism with this theory, but it’s fun to think about and it will be interesting to look back after the season to see how well it performed.
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