Zack Wheeler’s strikeouts rising with better pitch usage

Philadelphia Phillies right-hander Zack Wheeler has been one of the best starting pitchers in Major League Baseball this season. He owns a 2.52 ERA, 155 ERA+, and 2.46 FIP through 11 starts — the same number of starts he made in the pandemic-shortened 2020 season. His 2.9 WAR is tied-for-sixth in the majors and fifth among pitchers.

Fresh off three straight double-digit strikeout games — including a career-high 14 against the Tampa Bay Rays on Saturday — Wheeler ranks third in the National League with 92 strikeouts and is sixth in the NL with an 11.04 K/9 ratio.

If he was pitching like this in a contract year, he’d likely get north of a $30 million average annual value in free agency. He’s been the Phillies’ most valuable player in the second of a five-year deal as continues to rise from an above-average No. 2 starter to a legitimate ace.

Ben Clemens of FanGraphs recently went in-depth on how the 30-year-old has quietly improved this season. The biggest difference for Wheeler, Clemens explains, is his career-high strikeout rate that stems largely from a more effective use of his pitch arsenal — especially when he gets two strikes on batters.

Phillies RHP Zack Wheeler: Strikeout percentage, 2019-2021

Wheeler has always had strikeout stuff, but he’s never been a “strikeout pitcher”…until this season.

• 2019: 23.6% (58th percentile)
• 2020: 18.4% (18th)
• 2021: 31.7% (85th)

Wheeler’s 18.4 percent strikeout rate in 2020 ranked just 49th among qualified starting pitchers while his 31.7 percent mark so far in 2021 ranks 11th in the majors. Wheeler’s strikeout percentage increase of 13.3 percentage points is the fourth-highest jump among all qualified pitchers this season and the highest jump among active starting pitchers.

Wheeler’s strikeout rate jump from the 18th percentile in 2020 to 85th in 2021 is even more impressive — considering his previous career-best ranking in the Statcast era (2015-present) was in the 61st percentile (2018).

His whiff percentage (overall swings and misses) is up as well, to a career-high 27.7 percent, after it sat between 21.8 and 24.5 from 2017-2020.

Wheeler uses all five of his pitches — fastball, sinker, slider, curveball, changeup — to get strikeouts. Looking at how often he throws each pitch gives us some insight into how he’s drastically improved his strikeout rate.

Wheeler Pitch Usage, 2019-2021

• 2019: FB – 30.0%, SL – 19.8%, SINK – 29.0%, CV – 10.0%, CH – 10.2%, SPL – 1%
• 2020: FB – 42.1%, SL – 15.9%, SINK – 23.7%, CV – 10.1%, CH – 8.3%
• 2021: FB – 45.7%, SL – 25.6%, SINK – 16.3%, CV – 7.9%, CH – 4.6%

Wheeler started using his fastball a lot more last season — his first with the Phillies — and has continued to rely on it in 2021. His slider usage is up significantly and his curveball, despite a lower usage rate this season, has arguably been his best pitch (more on that later).

Wheeler has cut his sinker use almost in half — nearing a career-low rate — since he left the Mets and he doesn’t use his change-up much, so we’ll focus on his other three pitches for this piece.