Adbert Alzolay has the worst lefty power problem in baseball

One of the few bright spots in a Cubs season that has seen the club sell aggressively at the trade deadline has been the emergence of Adbert Alzolay. Alzolay had been hovering near the top of the Cubs prospect lists since 2017 but a lat injury in 2018 hindered his development at Triple-A Iowa. In 2019, his arrival at Wrigley Field was met with a lot of excitement on the north side of Chicago. Alzolay was spectacular in a one-hit, four-inning outing against the Mets. His arrival also heralded the first home-grown pitching talent in recent years because the Cubs had struggled to draft and develop their own pitchers. While Alzolay struggled with control during his 2019 and 2020 stints with the MLB club, Carmen Ciardello at FanGraphs broke down how he overhauled his pitch mix and approach to hitters in 2021 to slash his walk rate this season.

But while Alzolay’s adjustments to improve control and limit walks has certainly been a success this season, a new problem has emerged for the pitcher. He’s giving up a lot of home runs. In fact, he’s got the highest HR/FB rate among starting pitchers who have thrown at least 100 innings this season:

I took a closer look at Alzolay’s home run issues and found that it’s more complex than merely giving up a lot of home runs on fly balls. After doing a bit of digging it became clear that his home run problem is almost entirely isolated to left-handed hitters. Of the 23 home runs he’s given up in 2021, 19 of them have been hit by lefties. I can hear some of you now, left-handed batters are always better against right-handed pitchers. That is true, but Alzolay’s splits are the most extreme in baseball. He’s given up more home runs to lefties than any other right-handed starter with at least 40 innings against lefties (Casey Mize is second at 16). It isn’t just raw numbers, though. Alzolay’s HR/FB is 31.1 percent (Mize is a distant second at 27.6 percent). Additionally, Alzolay’s wOBA against lefties is the highest in the league at .410. As a reminder, wOBA is just a fancy type of on-base percentage that gives you more credit for extra-base hits. I’m using it here because it clearly highlights the quality of contact Alzolay is giving up to lefities as opposed to righties:

To unravel this puzzle I started by looking at Alzolay’s pitch mix and hitter’s counts to see if I could identify a certain pitch or situation that accounted for his home run struggles with left-handed batters. First, let’s talk about pitch make up. Alzolay really sticks to a fourseam fastball/sinker/slider mix. As Ciardello noted in his analysis earlier this season:

Alzolay has turfed his curveball in favor of a slider, which is now his most-used pitch; he throws it close to 50% of the time. His changeup is also all but gone from his repertoire, as is the emphasis on his four-seam fastball, which is now his third most used pitch. The sinker is his second most common offering at almost 30%, which flies in the face of how many teams look to develop their pitchers’ fastballs.

As a proportion of pitches thrown, batters from both sides of the plate do more damage against Alzolay’s sinker and fourseam than they do against his slider. Below you can see how his pitch makeup breaks down according to Statcast:

Statcast

Next let’s take a look at the proportion of long balls he gives up by pitch type:

Statcast

Alzolay throws his slider 40.8 percent of the time, but it only accounts for about 30.4 percent of the home runs hit off of him. The remainder are coming from his fourseam and sinker. Batters from both sides of the plate do a lot of damage on Alzolay’’s fastballs and it isn’t merely a home run problem. Both the sinker and fourseam have a much higher wOBA and xwOBA against them:

Like many pitchers, Alzolay gets into the most trouble when he’s behind the batter in deep counts. However, his splits as the counts get deeper are more pronounced than most pitchers. Admittedly, these are small sample sizes in some instances for Alzolay so I’ve included his innings pitched in each count so you can judge for yourself how much noise stems from sample size. However, even with that caveat it is pretty clear getting ahead of batters is abnormally important for Alzolay’s success. Below are batters’ wOBA against Alzolay by pitch count compared to the average among National League starters:

When Alzolay falls behind a batter 1-0, that batter’s expected wOBA jumps 64 points more than it does against the league average starter. When he’s behind 2-0 it jumps 52 points. When Alzolay finds himself in a full count against batters their wOBA against him is 99 points higher than it is against the rest of the NL’s pitchers.

To get a better understanding of what is happening during these at bats I went back and watched every home run Alzolay has given up in 2021 and found that he’s more likely to give up a long ball when he misses his spot. Lefties likely see these misses more clearly than their right-handed counterparts and do more damage on them accordingly. Take, for example, Cody Bellinger’s two-run shot off Alzolay on June 27. Alzolay is behind in the count 2-0 and Willson Contreras clearly wants this ball down and away. Alzolay misses his spot considerably and the 92 mile per hour fastball sails up in the zone before Bellinger cranks it out [VIDEO].

You can see a similar result, albeit in a friendlier count, with this Joey Votto solo shot in July. Contreras sets up at the top of the zone on the inside part of the plate. Instead, this 95 mile per hour fastball winds up in the heart of the zone and Votto crushes that mistake to straightaway center [VIDEO].

Of the 23 home runs Alzolay has given up in 2021, 19 of them occurred on pitches where Alzolay significantly missed his spot. Of those, 17 were mistakes to left-handed batters.

Some of these mistakes likely account for Alzolay’s increased changeup usage against lefties against the White Sox. He clearly needs an offering other than the sinker/fourseam for left handed batters. Giving up a home run on 35.1 percent of the hits he gives up to left handed batters is not a sustainable situation.

The good news for Alzolay and Cubs fans is with the Cubs out of contention Alzolay will get more opportunities to pitch deeper in games and work through the issues that may be leading to him missing his spots. For now, however, it seems clear that while Alzolay’s improved control has limited the number of walks he gives up, he hasn’t yet honed that control to hit his spots in and around the strike zone consistently. Left-handed batters are seeing those mistakes clearly and it’s led to a lot of home runs.

Alzolay is starting tonight in Miami against the Marlins. Here’s hoping for better results.