Earlier this year, I wrote about Outs Above Average (OAA), Baseball Savant’s tool for judging outfield effectiveness based on ranking players’ successes at catching balls classified by catch difficulty.

I’ve continued to follow that metric throughout the season, though I’ve also become intrigued by social media arguments that now is the time to trade Ian Desmond, who is having his best season since joining the Rockies. That said, I wanted to explore two questions: One, how is the 2019 outfield as compared to the 2018 outfield? Two, what is Desmond’s value to the Rockies?

The Rockies outfield

As of July 19, based on the Rockies’ team OAA, they are 28th in MLB with an OAA of -8. For comparison, the best defensive outfield as determined by OAA is the Washington Nationals, with an OAA of 17, while the Florida Marlins are the worst, with an OAA of -13. In 2018, the Rockies finished 25th in the league with an OAA of -14. Bear in mind that comparing the 2018 and 2019 outfields is inexact given that we only have just over half of the data for the 2019 team while having all of the data for the 2018 team. But if the Rockies play the same outfield defense in the second half of 2019, we could project a final OAA of -16, which means that the 2019 Rockies are on track to have a slightly worse defensive outfield.*

Now consider individual Rockies in terms of OAA. I’ve included the numbers from the article I wrote on May 27 to provide context in terms of whether a player has improved or gotten worse since that date.

Rockies 2019 OAA Player May 27 OAA May 27 MLB Rank — July 19 OAA July 19 MLB Rank Player May 27 OAA May 27 MLB Rank — July 19 OAA July 19 MLB Rank Tapia 2 27 — 2 30 Dahl 2 29 — 2 38 Desmond -1 66 — -6 83 Blackmon -2 77 — -7 85

For the sake of an imperfect comparison, at the conclusion of the 2018 season, Carlos González had an OAA of 2; Gerardo Parra’s was -2; Charlie Blackmon’s was -8.

These data show a few things. First, David Dahl and Raimel Tapia remain largely unchanged in terms of OAA, and they are clearly the Rockies’ best outfielders, though they have dropped in terms of MLB ranking since May. They are also as good as González was at the end of 2018 and significantly better than Parra.

Both Blackmon and Desmond have gotten significantly worse in their outfield defense. They are less effective than Parra, and Blackmon is on track to have a markedly worse 2019. Whether this is a question of a challenging outfield or age (both are 33 compared to Dahl and Tapia, who are 25) is a separate question. But the fact remains that both are defensive liabilities. The extent to which the outfield has put pressure on an already-stressed pitching staff is another key question.

That does not mean the Rockies should trade Desmond. He has contributed to an outfield that is less bad than it was in 2019. And as the Purple Dinosaur Podcast pointed out, there’s probably not a team interested in trading for him anyway. In other words, Desmond is a marginally positive defensive force for the 2019 Rockies, assuming that the defensive work of Dahl and Tapia continue to offset that of Desmond and Blackmon.

The Rockies outfield offense

Now consider what these outfielders bring in terms of offense:

Rockies Outfielders’ Slashlines Player 2018 Slashline 19 July 2019 Slashine Player 2018 Slashline 19 July 2019 Slashine Blackmon .291/.358/.502 .318/.365/.600 Dahl .273/.325/.534 .303/.350/.523 Desmond .236/.307/.422 .269/.322/.495 Tapia .200/.259/.480 .276/.314/.460

The 2019 outfielders are hitting significantly better than the outfield of 2018. Compare these numbers to those of 2018 Gerardo Parra (.284/.342/.372) and Carlos González (.276/.329/.467). Thus far, the 2019 outfield is collectively stronger offensively.

In terms of both defense and offense, the 2019 outfield is better than it was in 2018, suggesting that Ian Desmond is worth more to the Rockies on their roster than as a trade piece — and given that there’s no indication the Rockies will be buyers, keeping Desmond in Colorado seems like a foregone conclusion.

*CORRECTION: This article originally mis-stated that the 2019 Rockies (-16 OAA) were on track to have “a significantly less bad outfield” than the 2018 Rockies (-14 OAA).