When the 2007 season came to a close the Tigers had a top priority on their to-do list and that was to get a shortstop. Carlos Guillen’s knees and inconsistency making the routine play had dictated a move across the diamond to first base. So Dave Dombrowski moved swiftly to upgrade the infield defense while keeping a decent bat in the lineup by acquiring Edgar Renteria. Yet to listen to Tigers fans this year you’d think that they had pulled one of those statues down off the left field wall and positioned it between second and third. The fact of the matter is that Renteria is an average defender.
Renteria has picked up gold gloves in the past, but his last one was in 2003. On the wrong side of 30 it’s only natural to expect a shortstop to lose a couple steps and a little pop in the arm. Now measuring defense can be a tricky proposition. Mainstream fielding stats like fielding percentage and range factor and zone rating all have significant limitations in that they are either highly subjective, or highly dependent on context (types of pitchers, handedness or pitchers). Fortunately more advanced stats like ultimate zone rating (UZR), probabilistic model of range (PMR), and John Dewan’s +/- system improve upon many of the problems of the conventional stats. The downside is that they aren’t as readily available in season.
So we’ll start by looking at 2007 data to see what we should have expected form Renteria in 2008. Detroit Tiger Tales did a thorough analysis of defense combining all the defensive metrics he could find. The various metrics aren’t always in lockstep agreement, so instead of relying on one metric Lee looked at all of them and compiled shortstop rankings for the ’07 season. Lee’s study showed Renteria to be -3 runs below average, so slightly below average. Still it was a 14 run improvement over Carlos Guillen which equates to about a win and a half.
David Pinto, the creator of PMR, also produces charts showing how fielders do by the direction the ball is hit. The chart for Renteria shows that he is below average in the hole, but above average up the middle. This is consistent with John Dewan’s +/- ratings. In 2005 and 2006 he was -17 and -19 plays on balls to his right and +18 on balls to his left. If he’s worried about his arm he is probably positioning himself more up the middle knowing he’s more likely to be able to convert the balls he gets to into outs.
So now that we have an idea of what we should have expected from Renteria, what’s he actually doing this year? Using +/- data available from Bill James Online he is -3 plays on balls to his right and +3 on balls to his right. He ranks as the 13th best defender using this method.
PMR isn’t available until after the season. There was limited UZR data made available with the top and bottom fielders at each position and Renteria did make either list meaning he’s somewhere in the middle.
Looking at RZR (revised zone rating) he ranks 7th out of the 12 qualified shortstops in the AL.
Time and time again it looks like Renteria is a middle of the pack defender. He’s on the wrong side of the middle, but far from the catastrophe that many have made him out to be. And he’s pretty much exactly what he has been for the past few years. A guy without remarkable range but someone who makes the plays on the balls he gets to.