I watched a show called Baseball Seasons 1984 on MLB Network a few days ago. At the 21-minute mark there was a clip of Willie Hernandez pitching to Jim Rice with Wade Boggs at first in the ninth inning of a game played on April 13. Rice hit a two-hopper to Whitaker who started a 4-6-3 double play. Back in the day, such an occurrence was a familiar sight and fell well short of a cause for celebration. But having recently survived the 2012 season, I responded like a sugar-deprived kid without adult supervision on Halloween. Thanks to the miracle of the DVR I replayed this 4-6-3 over and over with an increasing sense of appreciation. Every path of man and baseball looked like the solution of a kinematic optimization problem. There was zero wasted motion. Whitaker and Trammell made prima ballerinas look clumsy, atomic clocks look out of sync.
Back to reality. The Tigers are said to be interested in Stephen Drew and the predominant storyline is that Drew's range will help the Detroit defense. Drew is about 290 days younger than Peralta and he looks more like a shortstop. The regression experts will tell you that Drew's body should decline slower. And when we look at offense, the Bill James 2013 projection has JP with an inconsequential edge in the two numbers that I look at first: wOBA (.326 to .320) and OBP (.329 to .325). So what about defense? The rest of this post will call upon defensive numbers that are still evolving so insert the standard disclaimer here and read forward at your own peril.
The defensive statistic that I start with for infielders is Fielding Bible +/- and the Tiger with the odd consonant placement has an edge of a few plays over Drew at shortstop for each of the last three years. But there's more to the story. We can break down the Fielding Bible ratings based on the distribution of batted balls. The conclusion is that Peralta is good making plays on balls to his left and poor at making plays to his right. Drew is the mirror opposite. For those who like numbers, Peralta was 6 plays below average going to his right and 12 plays above average going to his left between 2009 to 2011. Drew was 21 plays better than average going to his right but 15 plays below average going to his left over the same time period. Both were above average on balls hit straight on with Peralta holding a 7 play advantage over the three years.
It's no secret that Detroit's MVP at third base has below average range and that a shortstop like Drew can help cover this deficiency by making plays to his right on balls that Cabrera can't reach. The 56 zone, also less formally referred to as the 5.5 hole when discussing Tony Gwynn, is the angular slice of infield between the standard shortstop and third base positions. The Tigers allowed a .296 batting average on balls hit to this zone in 2012 which was the highest rate in the AL and well above the .248 ML average. The Oakland Athletics allowed just a .192 average on balls in this zone during the time that Stephen Drew was with the team which would have ranked best in MLB over the full season.
How big a deal is this? The Tiger pitching staff is mostly right-handed and they led the American League in strikeout rate this year. These factors work against the accumulation of balls to the left side and, sure enough, Detroit pitchers allowed only 388 balls into the 56 zone which was the fewest in the American League. Porcello led the club with 73 of these batted balls and Fister was a distant second at 52. The masochists among you may want to imagine how Wandy Rodriguez, a lefty with groundball and low K tendencies, might have fared with a Peralta/Cabrera left side in 2012 and his ML-leading 108 balls allowed into the 56 zone.
If we prorate the 2009-2011 numbers to a full season, then Peralta is about 20.7 plays per year better than Drew on balls straight on or to his left. If we use these numbers to project forward then on 388 balls the breakeven point for this whole story works out to allowing a .243 batting average in the 56 zone. If Drew can improve the Tigers to near where he was able to get the A's last year in the 56 zone with a rangier third baseman then Drew looks like a big win for the Tigers. If he gets the Tigers to around league average then it looks like a wash. And if Peralta declines faster as suggested above then Drew looks even better. Assuming that Mr. Drew can stay healthy.
Now excuse me while I go watch that Whitaker/Trammell double play again.