Does Nolan Arenado have a pop-up problem?

The first season of Nolan Arenado’s campaign in St. Louis came with all the things we’ve come to expect from the superstar third baseman. Superb defense:

And that superb defense comes with a very solid offensive season in which he tallied 34 HR and 105 RBI en route to a 113 wRC+ was certainly a season Cardinals fans could be happy with.

There were points in the season, however, where it seemed like Cardinals fans saw a lot of this:

The words “Arenado” and “popup” started appearing more frequently together in game thread comments, and game-to-game it seemed like the narrative was hard to refute. Arenado’s hit a lot of popups in 2021. As most VEB regulars know, though, the game threads tend to be a bit . . . reactionary. It’s part of what makes them two parts fun and one part ridiculous. I think everyone realizes that this qualifies as a nitpick looking back at an above-average offensive season, but the question of Arenado’s popup tendencies is one that I thought would be interesting to look deeper into.

To start, let’s look at Arenado’s batted ball profile starting in 2015 when statcast data became available with Baseball Savant.

Observation number one: Arenado is a very good player and has been for a long time now. With that being said, his popup rate hovers at just above 10%, slightly above the 7.1% that Baseball Savant lists as MLB average. So it turns out that Arenado does tend to hit slightly more popups than the average MLB player. There are a couple of years above that break this trend, though. The season that really drew my attention was the 2018 season, where Arenado posted his lowest popup rate at 8.6% and his highest wRC+ at 130.

After seeing the above values, I thought it might be interesting to look into the differences between Arenado’s 2021 and 2018 seasons. While he was good in 2021, he was dominant in 2018. And while there are other differences in his batted ball profiles between the two seasons (more on that later), the popup rates are something that could help explain the difference. Digging into the numbers more, I plotted each of Arenado’s batted ball events by their exit velocity and launch angle and color-coded them by recorded batted-ball type for both seasons.

The plot for the 2021 season shows a lot more balls hit at more extreme positive and negative launch angles while the 2018 data shows a much tighter distribution, suggesting that Arenado indeed squared the ball up more often in general for all hit types in 2018. Another difference is harder to spot though, and would probably only be noticed after looking at the table above. Arenado hit a much larger percentage of flyballs in 2021 (32.7%) than he did in 2018 (24.4%). Is that enough to account for the differences between the two seasons? Maybe, but there are other factors that can be considered.

One such factor is the types of pitches Arenado tends to swing at. It makes sense to think that a player that hits more popups than normal might chase more high pitches or have trouble reaching pitches high in the zone, especially when they’re in on the hands. In an attempt to visualize a similar trend for Arenado, I plotted each pitch location and pitch type that he popped up for both seasons.

The results were somewhat surprising. A lot of Arenado’s popups in both years came off of “mistake” pitches rather than borderline high or high pitches. What’s more, most of the popups in 2021 came off of fastballs lower in the zone. Below shows a more detailed look at the kind of pitches Arenado was most likely to pop up in each year.

Consistently, Arenado popped up the most fastballs (which wasn’t surprising given their tendency to ride high through the zone), sinkers, and sliders (both of which were surprising given those both tend to drop vertically). These results are reminiscent of an article in January written by J.P. Hill titled “Nolan Arenado: 4 Stats that Matter,” which included this commentary on Arenado vs fastballs in 2021:

“Like Goldschmidt, Arenado had a well-established history of crushing fastballs. His average wOBA against the pitch type through his prime seasons would be somewhere in the .425 range. Last season that fell to .306.

Why? What causes a wOBA drop of over 100 points against a pitch type? Was it the residual effect of his shoulder injury in 2020? Was it more of those BABIP issues showing up? Was he too homer (flyball) happy? Or was it just some combination of these things plus a healthy dose of statistical volatility?”

The issue here isn’t that Arenado pops up more fastballs than any other pitch; I think fastballs would dominate the above distribution for almost every batter. The fact he was popping up a good portion of them lower in the zone is a little more out of the ordinary and might be one of the indicators in how Arenado might have changed his approach since coming to St. Louis. J.P.’s mention of Arenado getting flyball happy in 2021 certainly could hold some water. The statcast data definitely seems to suggest it and it would theoretically make sense that 34 home runs from that approach would come with more flyouts and popouts as seen above.

The real question is this: if Arenado has changed his approach to prioritize flyballs and it leads to about 20 more popouts than he had in one of his best seasons, is that really a bad thing? Arenado has a lot of natural talents, but speed isn’t one of them. With runners on, I prefer the flyout to the double play. And, if he continues to produce as he did offensively and he squares up more fastballs as J.P. also hypothesizes in the above article, we’ll be seeing a number even better than 113 for his 2022 wRC+.

So yes, Arenado does in fact hit slightly more popups than is average. But as long as he puts up the kind of numbers we’re used to seeing from him, it’s definitely not anything to worry about.