By the Numbers: a different Zack Wheeler

Although the Philadelphia Phillies did not have the success they anticipated during the 2020 MLB season, Zack Wheeler certainly did. 

The accomplishment of the former New York Met at the onset of a five-year, $118 million contract, to some, might come as a surprise. After all, $118 million might be perceived as an overpay for a pitcher with a 3.77 career ERA from 2013-19, only one year of 190+ innings pitched and a Tommy John Surgery stint to his name. 

Shortened 2020 season aside, Wheeler performed extremely well over the course of the year. Starting with the basics, the 30-year-old righty went 4-2 with a career-best 2.92 ERA in 71.0 innings pitched (11 games started). Among all 2020 Philadelphia starters with a minimum of 30.0 innings pitched, Wheeler’s ERA was the best and easily trumped the 3.28 ERA of staff ace Aaron Nola. Additionally, among 16 MLB starters who pitched to a minimum of 70.0 innings, Wheeler’s ERA ranked seventh and was ahead of notoriously filthier pitchers, including Luis Castillo (3.21) and Lucas Giolito (3.48). 

From an ERA and innings standpoint, Wheeler was solid by all stretches of the mind – no doubt about that. 

Looking deeper, however, shows a pitcher going against the usual starting pitcher norm.

What does this mean? Well, let’s look into it, shall we? 

Let’s start with Wheeler’s strikeouts per nine (K/9) numbers. Over the course of the 2020 season, Wheeler accumulated a 6.72 K/9, which was a career low. Before the 2020 season, Wheeler’s average K/9 in five seasons (2013-19 without playing in 2015 and 2016) was 8.58. Among all pitchers during the 2020 season, the average K/9 was 9.10. Furthermore, his home run per nine (HR/9) numbers were also excellent. His 2020 HR/9 of 0.38 was easily a career high and leaps and bounds ahead of his average over his five previous seasons (0.97). The average HR/9 among all pitchers in 2020? 1.40

But wait, there is more. 

Wheeler’s 2020 groundball percentage (GB%) of 55.9% was also the highest of his career (his average before 2020 was 46.4%). To top it all off, Wheeler’s exit velocity (EV) against his pitches was 85.8 miles per hour, which was the lowest of his career since the statistic started to be tracked during the 2017 season. His average exit velocity from the 2017-19 season, meanwhile, was 86.9 mph. Then, there is his Fielding Independent Pitching (FIP), which takes strikeout and home run numbers into account. Although Wheeler’s K/9 was easily below league average, his 3.22 FIP was well ahead of the league average FIP (4.48). 

In other words, Wheeler was much better on the mound when he was not striking out batters.

Before transitioning into how Wheeler made this transformation, it is best to see where all of these numbers rank when compared to other starters. When looking back at the 70.0 inning limit among 2020 starters, Wheeler’s 6.72 K/9 ranked 14th out of 16 qualified pitchers. While this is definitely a low total, everything else was very, very good. His 0.38 HR/9 and 85.8 EV ranked first, while his 55.9 GB% ranked second. Then, there is his 3.22 FIP, which ranked eighth. 

Let’s recap everything so far. Wheeler, despite possessing sub-par strikeout numbers, put together excellent home run, groundball, exit velocity numbers and FIP numbers, so much, in fact, that Wheeler put himself in the same category as other elite pitchers in terms of overall production. 

The question still remains. How did this transformation come to be? How did a pitcher go from modest strikeout and home run totals to the polar opposite? 

To best notice the difference, let’s compare Wheeler’s 2020 season to his final season with the Mets (2019).  

When comparing Wheeler’s 2019 pitch usage to his 2020 pitch usage, the first thing to stand out is his four-seam fastball usage, which increased from 30.0% in 2019 to 42.1% in 2020. The increased usage in his four-seamer, as a result, decreased his sinker and slider reliability. His sinker usage decreased from 29.0% usage to 23.7%, while his slider dipped from 19.8% to 15.9%. 

His increased four-seamer usage all over the zone, in effect, threw batters for a loop, despite having a lower whiff percentage (Whiff%) in 2020 compared to 2019 (27.1% to 20.0%). A slightly lower spin rate on his fastballs (ranking in the 59th percentile in 2019 to 52nd percentile in 2020) also makes for an intriguing situation. 

The end result for Wheeler’s 2020 transformation, in total, boils down to simply having more confidence in his four-seamer, and who would blame him? His average four-seamer velocity was a hair higher in 2020 than 2019 (96.8 mph to 96.9 mph) and ranked in the 94th percentile in all of MLB during 2020. 

Sure, the numbers can suggest where the change occurred, but how the change occurred was simple – confidence, even if the pitch was not picking up a ton of swings and misses. 

Even with a shortened season and a much smaller sample size, Wheeler’s 2020 season showed promise as both the player and the franchise get into the meat of the big-money contract. Should he continue the production, he will be worth every penny, low-strikeout totals or not. 

Although Philadelphia did not have the overall success they wished for in 2020, Wheeler did, and should he continue to do what he did in future seasons, Philadelphia will not complain. 

Not one bit. 

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