Ronald Acuna Jr. Defense - Video Evidence
Let me start by directing you to a really cool page. The fielding section of Ronald Acuna Jr.'s Baseball Savant player page. If you scroll down, you can see a chart showing the catch probability for Acuna's plays this season.
Now, I would like to direct your eyeballs to video evidence of plays Acuna didn't make that most major-league outfielders would have.
Exhibit A - Acuna Can't Make the Play on a High Fly with 99% Catch Probability
Exhibit A - The catch probability on (the video is in the "Exhibit A" link) Exhibit A is 99%. So watch the video and just know that based on the distance he needed to travel and the time the ball was in the air, 99% of major-league outfielders would have made this play.
You can see Acuna makes a bad read backward, then he freezes for an odd amount of time and then goes on a sprint toward the ball. Even the announcers were shocked. This is a good example because a lot of camera shots don't cut to the outfielder quickly enough to show the initial read.
Exhibit B - Acuna Pulls up on Flyball with 99% Catch Probability
Exhibit B - Here Acuna pulls up on a ball that most players would catch. I included this one because we have seen this a lot from Acuna this year. They aren't always on 95% catch probabilities, but this one is.
Exhibit C - Acuna Gives Jason Heyward a Hit by Pulling up on Flyball with 95% Catch Probability.
Exhibit C - Here is the ball he pulled up on against the Dodgers. Jason Heyward hit a "routine flyball" as the announcer said. Acuna pulled up and let it fall. This is a ball most major-league outfielders are going to catch. When I saw Acuna stop short on this ball on Sunday, it brought back memories of the research I had done. That ball should have been caught, especially with Acuna's speed.