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What's Up With...? Arizona's Defense

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"If we're going to preach pounding the strike zone to our pitching staff, we need to have a defense behind it that can catch the baseball. I don't want to just get better... I want to blow that number out of the clubhouse. Making plays was difficult for us at times, and it cost us games."
-- AJ Hinch, February 2010

Improving the Diamondbacks' defense was made a clear priority for the team, even before spring training got under way. Now we're into the second third of the season, is the team living up to those expectations? Are we indeed "blowing that number out of the clubhouse"? After the jump, we'll take a look at the numbers.


The bluntest instrument in the fielding metrics box is errors - a largely subjective measure, but one which was still a serious problem for the Diamondbacks in 2009, where they committed 124 over the year, more than any other team in the league bar Washington, some of them very embarrassing gaffes. That number has certainly improved - to date, only 37 errors by Arizona, fifth-fewest in the National League. If they maintain that pace the rest of the way, it would give them 92 for the year, their lowest total since 2002 (89).

This overall improvement conceals a wide variation by position, where the projected numbers range from less than one-fifth of last year's error total, to half as many again. Breaking down the errors by position, to see where the improvement has taken place, here are the numbers: so far, pro-rated and compared to 2009.

Position 2010
so far
2009 vs.
Catcher 1 2.5 9 27.7%
1st Base 7 17.4 15 116.3%
2nd Base 7 17.4 11 158.6%
Short-Stop 5 12.5 16 77.9%
3rd Base 5 12.5 27 46.2%
Left Field 1 2.5 9 27.7%
Center Field 3 7.5 5 149.5%
Right Field 1 2.5 13 19.2%
Pitcher 7 17.4 19 91.8%

On first glance, left field, right field and catcher are the big areas of improvement, with third base also a lot better. Center-field and second base have taken a step back. There's some truth to that: Mark Reynolds is clearly not as error-prone as he was, and Justin Upton has largely avoided the silly mental errors which reduced Arizona fans to frothing apoplexy in 2009. I'm not quite as convinced by our catchers, because the number of wild pitches and passed balls tell a very different story - no NL team has more of either. The Diamondbacks are on pace for fifteen PBs this year, almost double last year's total of eight..

The wild pitches are even more extreme. Last season, the Diamondbacks already led the league with 79, but they have so far thrown over half that number, and are on pace for a total of 100. That would appear to be unprecedented - the most I could find in all of baseball history was the 96 thrown by the 2000 Cincinnati Reds. Obviously, wild pitches are not entirely the catcher's fault, but over the course of a season, good defensive catchers will turn more of these into simple balls out of the strike-zone than bad catchers. In particular, Edwin Jackson has already thrown more wild pitches than in any other season of his career.

Defensive Efficiency

Put simply, this is the percentage of balls in play that get converted into outs by the defense. This metric is not quite as enamored of the Diamondbacks as raw errors. Overall, our defensive efficiency is 67.2%, thirteenth in the league and below NL average of 68.6%. However, due to park factors, it's not easy to compare across teams - obviously, a park with a large outfield is going to see a lower percentage of outs than a bandbox, even with the same players. But for an individual team, playing the majority of its games in the same parks, it can prove a useful measurement of how the defense is performing from year to year.

The bad news is, we're converting less balls into outs than we were in 2009 - the figure there was 68.3%. Indeed, this season's current DE figure is the lowest in franchise history. Again, this doesn't necessarily indicated a problem with defense, because the number is also tied to Batting Average on Balls in Play, which is known to have a significant random component. There, the Diamondbacks pitchers' have the third-highest BABIP in the NL, at .318, despite a line-drive rate which is basically very close to the league mark. If that regresses to the mean, it should help the DE improve a bit.

Advanced Metrics: UZR, FRAA and DRSAA

I'm not going to go into the details of how Ultimate Zone Rating, Total Zone Fielding Runs Above Average and Baseball Info Solutions's Defensive Runs Saved Above Average are calculated. Because there are not enough St. Penelope pictures available for me to sprinkle through the explanations, and still keep you awake. Click on the links if you care and/or need a cure for insomnia. However, all three do offer a method of comparing defensive play for the Diamondbacks this year and last. You should, however, note that defensive metrics are subject to significant random fluctuation - 40% of a season is a very small sample-size in such things.

Ultimate Zone Rating

The rate stat here is UZR/150, which is UZR per 150 games played. The Diamondbacks are currently sitting at +6.9, which is third-best in the NL and fourth in the majors. That is a significant improvement on last year's number of +0.6, sixth in the league. Breaking it down by individual positions is a little tricky because of the way has presented the data, but here are the UZR/150 numbers for the players are each position who played the most innings. There are no UZR numbers available for pitchers or catchers, so those two spots are not included in the table:

Position 2009 UZR/150 2010 UZR/150
1st Base Chad Tracy +0.3 Adam LaRoche +3.7
2nd Base Felipe Lopez +1.0 Kelly Johnson -6.0
Short-Stop Stephen Drew +3.1 Stephen Drew +2.8
3rd Base Mark Reynolds -7.4 Mark Reynolds +17.7
Left Field Gerardo Parra -4.1 Conor Jackson -1.4
Center Field Chris Young -7.4 Chris Young +4.9
Right Field Justin Upton +8.1 Justin Upton +13.8

The number that stands out is Reynolds, with the numbers here backing up what we say in the 'errors' section above. Mark's defense this season appears to be vastly improved - to the extent that UZR sees him as the best defender on the team in 2010, when he was close to the worst last year. His number is only beaten in the NL by Ryan Zimmerman (+24.7). Young is also back to the side we would expect - his 2008 number was positive, albeit barely at +0.2 - and Upton remains a solid defender. However, UZR appears to share the dim view of Johnson's ability at second-base.

Fielding Runs Above Average

This combines the various components, e.g. Rdp, Rcatch, etc. into one number for an overall defensive contribution, measured in runs saved compared to the average. The Diamondbacks in 2010 are currently sitting at -8, which ranks them eleventh in the league. That's down somewhat on last season, where they were at +8 over the whole season, good enough for sixth spot. Below is the chart breaking the number down, for all Diamondbacks at each position: here, we're looking at total FRAA per 1,200 innings, which is about 135 games. There's no number for the pitcher.

Position FRAA
Catcher -11 -20
1st Base -8 -12
2nd Base +3 -11
Short-stop +3 -6
3rd Base -11 -9
Left Field +6 +14
Center Field 0 +1
Right Field +25 +26

Again, some of these results tie in with what we would expect based on our observations, such as catcher and second-base being weaker defensively than they were in 2009. In general, FRAA does not like our infield at all, thinks shortstop (mostly Drew) is now below-average at the position, and is nowhere near as impressed with Reynolds' improvement as UZR was. On the other hand, it does appreciate our outfield so far, and particularly Upton, whose personal tally of +10 so far, is second in the league among all outfielders [the Mets' Angel Pagan is top-ranked, on +14].

Defensive Runs Above Average

Finally, there's the work of Baseball Info Solutions, who seem to rate the Arizona defense more positively in general. This year, they are rated at +20 to far, which is sixth in the NL. However, that is a step down from last season, when the Diamondbacks finished the year at +34, third-best. I have to say, that does make me go "Hmmm..." since I think few people would tend to have rated us as possessing such a high number last season. Even if less obvious factors such as range caused some players to be undervalued e.g. Reynolds and Upton, the sheer number of errors committed by the team would seem to negate these positives. Still, let's look at DRAA - again, per 1,200 innings - for last year and this, and see what we find.

Position DRAA
Catcher +2 -8
1st Base -11 -2
2nd Base 11 0
Short-stop +7 +8
3rd Base -3 +15
Left Field +12 +19
Center Field +3 +15
Right Field +10 +15
Pitcher -4 -19

Chalk up another vote for our catchers having bitten the big one defensively speaking. Second base has also declined, but both the corner infield spots appear to have improved. Again, this metric likes our outfield, but differs in that it rates left-field as our best position defensively. However, center has posted a significant improvement. This is the only one of the measurements which comes up with a number for our pitcher's fielding prowess, and it isn't a pretty picture.


There's a story about a group of blind men experiencing an elephant. One touches the tail and thinks it's a rope. Another a log, and believes it's a tree; another the trunk, and feels it's a snake; and so on. While a somewhat-odd story these days - the National Federation of the Blind is filing an injunction to prevent such clearly prejudicial treatment - it does relate to defensive metrics. Unlike, say, OPS for offense, there is no single number which you can point at and say, "This measures defensive skill." You need to look at fielding from multiple angles; if you get the same answer from them all, then you can start to draw conclusions.

Hence, polling all the numbers we've looked at in the previous section, here are five statements about the Arizona defense, in descending order of confidence:

  1. Our catchers have been a lot worse this season.
  2. Justin Upton is among the, if not the best defender on the team.
  3. Kelly Johnson is not as good at second as Felipe Lopez was.
  4. Mark Reynolds has improved this year, possibly greatly.
  5. Chris Young is looking better too.