How Zack Wheeler has ascended to postseason legend

In case you haven't noticed, the Phillies have sort of figured out playoff baseball in the past few seasons.

After winning 87 regular-season games in 2022, they made a surprise World Series appearance before losing in six games against the Astros. This season, there were no surprises or doubts about the 90-win Phillies, who have dominated their way to the cusp of their second straight World Series appearance.

Outside of Bryce Harper -- who has produced consecutive all-time great postseasons -- no Phillies player has carried this group as much as Zack Wheeler. The 33-year-old has blossomed into one of baseball's best pitchers since coming to the Phils from the Mets as a free agent following the 2019 season.

Impressive as Wheeler has been in the regular season, it's been his playoff dominance the past two seasons that has elevated his status to an even higher level and been a key reason for Philadelphia's success. After posting a 2.78 ERA and 33 strikeouts in 35 2/3 innings in last year's postseason, he's leveled up in three playoff games this year with a 2.37 ERA in 19 innings -- as well as a ridiculous 26-to-1 strikeout-to-walk ratio.

As the Phillies seek yet another World Series appearance, it's worth looking into what has made Wheeler an invaluable ace and one of the best pitchers in postseason history.

Going from regular-season ace to playoff stud

After pitching for the Mets from 2013-19 -- missing the 2015-16 seasons recovering from Tommy John surgery -- Wheeler signed a five-year, $118 million deal as a free agent with the Phillies in December 2019. Since that point, Wheeler has firmly established himself as one of the top aces in the sport.

Since 2020, Wheeler has led all qualified starters with 19.3 Wins Above Replacement (FanGraphs version) thanks to a combination of both quantity (629 2/3 innings) and quality (3.06 ERA and 2.90 FIP). Few pitchers have shown his level of dominance -- in terms of run prevention, stuff and command -- while doing so in this many innings. Somehow, one of baseball's best pitchers has found an even higher level in October after reaching the playoffs for the first time in 2022.

Regular season vs. postseason numbers since 2022

3.26 ERA (345 IP) / 2.63 ERA (54 2/3 IP)
1.06 WHIP / 0.70 WHIP
26.9% strikeout rate / 28.9% strikeout rate
5.2% walk rate / 3.9% walk rate
.277 xwOBA / .253 xwOBA

Wheeler's numbers aren't just good compared to his regular-season norms. They match up with pretty much any postseason pitcher. Among the 170 pitchers who've thrown 40 postseason innings, none has a lower WHIP (0.70) than Wheeler. He's just one of four pitchers in that same group who has a strikeout rate of at least 25% and a walk rate below 5% -- the others being other postseason legends themselves in Nathan Eovaldi, Stephen Strasburg and Cliff Lee.

Wheeler's keys to October dominance

We know that Wheeler is a dominant postseason force. The question is how he's doing so when the stakes are the highest against the best teams in the sport.

For Wheeler, the main reasons for the improvements in October are surprisingly simple. He's throwing harder, using his fastball more and getting ahead of hitters more frequently.

Across the past two postseasons, Wheeler has seen his velocity up nearly a full tick on both his four-seamer (96 mph) and two-seamer (96.0 mph). Ditto for his curveball (82.5 mph) and his slider (91.8 mph). While adrenaline generally leads to a sizable velocity boost for most pitchers in the playoffs, Wheeler isn't just seeing these positive returns in shorter outings. He's tossed at least five innings in all nine of his postseason starts.

Wheeler has responded to his velocity boost by throwing more fastballs, especially earlier in the count. His fastball usage has jumped 4.1% in the playoffs the past two seasons to 64.7%. More notably, Wheeler is throwing first-pitch fastballs 73% of the time in the playoffs compared to 67.1% in the regular season. Because he's throwing harder fastballs more often on the first pitch for strikes, he's seen his first-pitch strike rate jump from 63.9% in the regular season to 70.1% in the playoffs, including a whopping 73.9% rate in this year's postseason.

That's helped put Wheeler in a better position to do damage in optimal counts for a pitcher. When he's been ahead in the count in the postseason, opposing hitters have a measly .127/.136/.167 line against him. When Wheeler has gotten to two strikes, he's generated most of his strikeouts on his curveball (21), four-seamer (20) and a new sweeper (8) that he folded in prior to this season.

Sweeping his way to a higher level

A differentiating factor for the best athletes is their ability to constantly find new ways to improve. In the case of Wheeler -- who didn't exactly need to change that much -- he joined the sweeper craze by adding his own version in Spring Training this year.

"The sweeper is a pitch that Wheeler started to throw in Spring Training, hoping to give hitters something else to consider as they tried to beat him," MLB.com Phillies beat writer Todd Zolecki wrote after Wheeler's Game 1 Wild Card Series outing against the Marlins.

Despite the spectacular regular-season results with the pitch (39.2% whiff rate and .360 SLG), Wheeler's sweeper was his fourth-most utilized pitch at 12.2%. That's changed in his first two playoff outings this year, which has seen the usage jump to 21.6%. That has been Wheeler's second-most utilized pitch outside of his four-seamer. It was clear that the pitch itself and Wheeler's usage of it was different after his Wild Card Series start, where he struck out a career-high five batters on the sweeper.

“That was the best the sweeper’s been,” Wheeler said after his Game 1 against the Marlins.

The metrics back that up. Wheeler has seemingly found the optimal combination of velocity, spin and horizontal movement on the pitch in the playoffs. He's throwing it about a half-mph slower (83.8) in the postseason but is getting an additional 1.7 inches of horizontal break on the pitch. At 15.3 inches of break, it is moving almost the entire distance of the width of home plate (17 inches). Hitters have struck out eight times in 18 plate appearances ending on the sweeper, with Wheeler's only real mistake coming on Travis d'Arnaud's home run in his Game 1 NL Division Series start.

With a nastier sweeper at his disposal, Wheeler has been an even better version of his 2022 postseason self. It's not just the two different fastballs that consistently clock in at 97-plus mph and land for strikes. Nor is it just the already-strong breaking balls (slider and curveball) that he's been able to use to put hitters away. Now Wheeler is relying heavily on a breaking ball that can nearly cover the width of home plate.

Some pitchers have a knack for taking their game to the next level when October hits. It's become abundantly clear that Wheeler fits that criteria. After helping lead the Phillies to within two games of a World Series title last year, he's doing his best to make that happen again this year -- and then some.

If Wheeler keeps this up, the Phillies might be hoisting their first World Series trophy since 2008.