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Examining Yuli Gurriel’s Sudden Penchant for Walks

A plate approach change for the Astros’ first baseman?

MLB: Houston Astros at Los Angeles Angels Gary A. Vasquez-USA TODAY Sports

Yuli Gurriel has never been known for his ability to draw loads of walks. Even at his peak walk rate of 6 percent in 2019, Gurriel’s free pass numbers throughout his career are decidedly below-average. So, to my surprise, look at where the Astros’ first baseman is currently listed on the 2021 leaderboards when you filter by walks.

Top Ten 2021 Walk Rates

Player BB%
Player BB%
Joey Gallo 23.5%
Miguel Sano 23.2%
Luis Urias 23.1%
Mike Trout 21.3%
Robbie Grossman 20.0%
Freddie Freeman 19.7%
Max Muncy 19.4%
Yuli Gurriel 18.5%
Bryce Harper 18.0%
Jacob Stallings 18.0%
Note: Only Qualified Hitters FanGraphs

A general rule about walk rates is that it takes about 120 plate appearances for the sample to demonstrate some reliability. At this point in the season, with only 65 plate appearances to his credit, Gurriel is slightly more than halfway to that point. Now, to be clear, that 120 plate appearance figure doesn’t represent a magic threshold that we can use to predict the future walk rate for a hitter. What that plate appearance figure represents is the point where the walk rate is starting to become more stable and less about the influence of random chance. As additional data pours in with each passing game, the more we will know if this drastic spike in Gurriel’s 18.5 percent walk rate was for real or a random mirage in April.

For a hitter to dramatically increase their walk rate from one season to the next, we can assume that there was some sort of deliberate change to their approach. Like, was there a decision to be more selective? Are they chasing less outside of the zone? Or swinging less in general? There are a few different routes a hitter can take to improve their plate discipline.

In Gurriel’s case, who has generally posted excellent strikeout rates as a hitter, the spike in his walk rate thus far appears linked to a newfound willingness to swing less than ever before at 41.9 percent this season compared to his career average of 49.4 percent. Among hitters with at least 150 plate appearances, only six have swung less from one season to another — 2020 to 2021 — than Gurriel.

To go a bit further, where is Gurriel exactly swinging less? If he was swinging less inside and more outside of the strike zone, we would surely see a higher strikeout rate. But that isn’t the case in 2021 as his 10.8 percent rate matches his career average of 10.8 percent. That leaves only one possibility and we can thankfully separate Gurriel’s inside and outside swing rates to confirm this hunch.

I think it is safe to assume that Gurriel’s spike in his walk rate can be directly attributed to his newfound ability to lay off pitches outside of the strike zone. In fact, it is specifically a better eye for fastballs and breaking pitches that he is chasing less and less.

Again, we’re only 15 games into the season for the Astros. An 18.5 percent walk rate for Gurriel is likely not sustainable across a full season or even multiple months. But it is interesting to see such a change in Gurriel’s plate discipline profile. It is encouraging to see that this walk rate spike might be grounded in an approach change. While I’m sure there is more to be written about this development, I’d rather wait until we have more data to make any concrete assumptions. So, for now, I wait.