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What two new stats say about the Rockies’ outfield defense

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Catch probability and Outs Above Average suggest the Rockies’ outfield defense has been just fine

During the offseason, I wrote about the Rockies’ outfield challenges. To summarize, I looked at slashlines and DRS and concluded that the Rockies’ production was lagging and that they needed to make a change. I recommended signing A.J. Pollock.

I wanted to return to that article and see how the Rockies are faring in terms of outfield defense given their 2019 adjustments. That said, I have become increasingly fascinated by Baseball Savant (a gorgeous, data-filled site), so I decided to see how the Rockies’ outfield compared as measured by catch probability and Outs Above Average (OAA). Some of what I learned surprised me; some was what I expected.

Catch probability

MLB.com defines “catch probability” as “tak[ing] the distance an outfielder must go, the time he has to get there, and the direction he travels to put a percentage of catch likelihood on each individual batted ball.”

To measure this, Baseball Savant has created five categories that classify catches based on difficulty, with a 5-Star catch being most difficult and a 1-Star being least difficult:

Level of Catch Difficulty

Level of Difficulty Catch probability
Level of Difficulty Catch probability
5 Star 0-25%
4 Star 26-50%
3 Star 51-75%
2 Star 76-90%
1 Star 91-95%

Here are the current catch probability numbers of the 2019 Rockies. Remember: At this point, we have only completed one-fourth of the season, so the numbers are not big.

Rockies Outfield Catch Probabilities (as of May 26, 2019)

Player 5-Star outs/opportunities/% 4-Star outs/opportunities/% 3-Star outs/opportunities/% 2-Star outs/opportunities/% 1-Star outs/opportunities/%
Player 5-Star outs/opportunities/% 4-Star outs/opportunities/% 3-Star outs/opportunities/% 2-Star outs/opportunities/% 1-Star outs/opportunities/%
Tapia 0/3 — 0% 2/6 — 33.3% 3/3 — 100% 5/5 — 100% 4/4 — 100%
Dahl 1/5 — 20% 1/1 — 100% 3/3 — 100% 4/7 -- 57.1% 5/5 — 100%
Desmond 0/4 — 0% 0/4 — 0% 1/3 -- 33.3% 5/6 -- 81.3% 7/7 -- 100%
Blackmon 0/5 — 0% 1/4 -- 25% 0/1 — 0% 7/8 -- 87.5% 7/7 -- 100%

What can we gather from this? A few things. The Rockies’ outfield has had 17 opportunities to make 5-Star catches, but only Dahl has been successful and only once. That shouldn’t be viewed as a bad thing, as they are by definition difficult plays, but it would be great to make more of them. Moreover, Dahl has also struggled a bit with relatively easy 2-Star catches. That said, both Dahl and Tapia excel at 3-Star plays. In general, the Rockies have had an average outfield that makes the easy plays but is less successful with challenging ones. It’s worth remembering that Blackmon is learning a new position while Desmond is returning to a position he has not played regularly since signing with the Rockies.

Outs Above Average

Catch probability data is used to generate an “Outs Above Average” number, which is “a range-based metric of skill that shows how many outs an outfielder has saved over his peers, accounting for not only the number of plays an outfielder makes (or doesn’t), but also the difficulty of them.” As Baseball Savant explains, “For example, a fielder who catches a 25% Catch Probability play gets +.75; one who fails to make the play gets -.25.”

Here’s how the 2019 Rockies rank in terms of OAA. I’ve included the 2018 season totals, though the difference in sample size makes the comparison a bit misleading. Also, Tapia and Dahl are not included in the 2018 numbers.

Rockies 2018 and 2019 OAA

Player in 2019 OAA MLB Rank
Player in 2019 OAA MLB Rank
Tapia 2 27
Dahl 2 29
Desmond -1 66
Blackmon -2 77
—-
Player in 2018
González 2 38
Parra -2 61
Blackmon -8 82

To provide some context, currently Byron Buxton and Lorenzo Cain are tied as the most highly ranked outfielders with an OAA of 9. Makes sense. Last year, it was Cain with a final OAA of 22. That makes sense, too. Thus far in 2019, the poorest outfielder according to OAA is Domingo Santana, #99 with an OAA of -8.

We can draw a few conclusions from this. First, the Rockies, are slightly above average this year defensively and on track to be better than they were last year. Second, the Rockies’ concerns about Tapia’s defense have turned out to be a non-issue. In fact, he is the best fielder the Rockies have this year and is, to this point, an improvement over Gerardo Parra. That said, David Dahl’s fielding is improving. (He had an OAA of 1 when I began writing this article.) Third, while Desmond still has a negative OAA, he is significantly better than Blackmon was in center field. Fourth, although Blackmon is not as good as Carlos González in right, he is much improved over his 2018 performance in center field even though he still has a negative score.

As a team, the Rockies currently rank 11th with an OAA of 2, placing them third in the NL West. In 2018, the Rockies finished with an OAA of -14 for an MLB ranking of 24th, so at this point, they are a significantly better team in terms of outfield defense.

Oh, and AJ Pollock, the now-Dodger that I urged the Rockies to sign? He’s on the IL and has an OAA of -2 — ranked #83, right behind Charlie Blackmon.