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An Update on Defensive Metrics for the Astros

Over a month ago, I wrote an article, based on the Hardball Times' Revised Zone Rating (RZR), describing the Astros' apparent defensive improvement during the first month or so of the season. LINK   I have been meaning to update the range-based defensive metrics to see if the Astros' positive trend is continuing.

Maybe this is as good as any time to look at the defensive metrics.  The Astros have been losing on this homestand so far, and this article diverts my attention to a more abstract subject.  Also, we have information from additional methodologies to add to the mix.  Mitchel Lichtman released selected data from his Ultimate Zone Rating (UZR) system. LINK  In additional Bill James' web site publishes information (subscription basis) based on John Dewan's +/- system (made famous by the book, The Fielding Bible).  So, we can check some of the RZR results for consistency with other methods.  As always, the sample size caveat applies this early in the season.

The Astros' poor record in 2007 has been attributed, in part, to the team's bad defense, which made the team's pitching worse than it should be.  The Astros' management acknowledged the team's defensive shortcomings in 2007 and vowed, during the off-season, to improve the team's defense.  The primary changes in personnel to accomplish that improvement : adding Bourn to CF and moving Pence to RF; replacing a Loretta/Bruntlett platoon at shortstop (after Everett's injury) with Tejada; replacing Biggio at 2d base with Kaz Matsui; and adding two good glove players (Erstad and Blum) to the bench.  Before the season started, it's fair to say that many posters on this board (including me) were skeptical that the changes would be enough to result in a good defensive team.

However, the RZR results after the first month were consistent with a greatly improved defense.  Although the Astros' team RZR results have slipped slightly, in absolute terms, since my first article, the Astros continue to have the third best RZR ranking in the NL, behind only the Cardinals and Padres.  (Hardball Times team stats here.)  The Astros infield RZR is ranked 3d and the outfield RZR is ranked 4th.

The Astros' team UZR results (expressed in runs above or below average) indicate a NL ranking of 5th.  Lichtman's blog shows the difference between actual team UZR results so far and the UZR results he would have projected for the team during the preseason.  The Astros' difference between actual results and preseason projection (29 runs) is the second largest among ML teams.  The Astros' defense is 14 runs above average so far, and Lichtman says he would have projected 15 runs below average at this point.  So, UZR's results confirm that the Astros' defense has performed a lot better than we expected.  The Astros' UZR result suggests that the team ERA might be roughly 4.59, instead of the actual 4.34 ERA, if the team had not played above average defense.  (Note that a 4.59 ERA would be close to the team's Fielding Independent Pitching rate of 4.56.) Without the defensive improvement, the Astros NL ERA ranking would fall from 6th to last.

St. Louis' excellent defense so far this season has allowed that team to achieve a good 3.90 ERA, despite a spotty starting pitching corps.  The Astros' pitching staff has also been shaky, and it is scary to think where the team would be without the defensive improvement.  However, the Achilles Heel of the Astros' pitching this season has been the home run; the Astros are currently on a record setting pace for allowing home runs.  Unfortunately, the fielders can do very little to help the pitchers avoid home runs. (Michael Bourn provided a rare example of doing so in the last Brewers games, when he made a spectacular play on a long fly to deep center which appeared on its way out of the ballpark.)  If the Astros defense regresses very much, as some people might expect, the quality of pitching could become very bad.  I can't say if the defense will regress or not, but it is something to think about when we see the next critical defensive misplay cost the Astros a game.

Here are the individual Astros player results.  The Dewan +/- results ("Fielding Bible" method) are expressed as major league rankings, while the RZR results are expressed as NL rankings.  Lichtman only provides "top 5" and "bottom 5" individual rankings (major leagues); so I can only reference a UZR top 5 or bottom 5 result.

(RZR NL rank; Fielding Bible ML rank; UZR rank, if known)

1st base. Berkman: 1st; 1st; 2d.

2d base: Matsui: 8th; 22d; tied for last

3d base: Wigginton: 7th; 29th; unknown.

Shortstop: Tejada: 1st; 11th; 3d.

LF: Lee: 10th (last); 10th (above average); unknown.

CF: Bourn: 5th; 3d; unknown.

RF: Pence: 2d; 2d; unknown.

How much more can Lance Berkman do?  He is having an incredible offensive season. And, by every account (including my observation, as well as the metrics), he is playing superb, gold glove quality defense at first base.  If he keeps this up, he should be considered a definite league MVP candidate.  Although Berkman has played worse defense in previous seasons, I know of no physical reason why he can't continue his excellent defense.  A guy who has started in CF and RF earlier in his career should be capable of playing good defense at 1st base.

Matsui's defense has been disappointing, particularly given his good fielding last season.  Based on what I have seen, Matsui's main problems have arisen from trying to make the impossible play.  He also has committed too many errors.  However, Matsui has also made some spectacular, acrobatic defensive plays, which indicate that he is capable of moving upward in the defensive rankings by season end.

Tejada has provided much better defense at shortstop than we expected based upon the reports out of Baltimore that he had diminished range.  RZR ranks him the best shortstop in the NL.  However, considering both out of zone plays and RZR, Atlanta's Escobar may be playing better defense than Tejada.

Wigginton and Lee have both been predictable weak links in the defense. Wigginton is mediocre, according to RZR, while the Dewan +/- system indicates that he may be one of the worst 3d baseman in the majors.  At least, neither Lee or Wiggy were in the bottom 5 of the  UZR rankings.    Lee is the worst NL LFer, according to RZR, but he is slightly above average (+2), according to Dewan's system.

Based on observation, Bourn would seem to be the biggest improvement in the Astros' defense; I'm sure that sense is enhanced by the thrill of seeing world class speed racing in the outfield.  Bourn is ranked as the 5th best NL CFer, according to RZR.  He is the 3d best CFer in both leagues, according to Dewan's system.  Bourn's RZR results have shown the most decline since my article last month.

Moving Pence from CF to RF has proven to be a very good decision.  Pence was a decent, but not great, defensive centerfielder.  He is now one of the best defensive RFers in the major leagues.

I'll try to update these defensive results later in the year.