Power play: Harper flips switch on slider struggles

Bryce Harper is crushing everything this postseason, including the pitches that were his biggest weakness during the regular season.

Harper has teed off against the D-backs' fastballs in the National League Championship Series. Just watch his monster home run off Zac Gallen in the Phillies' win in Game 5 to see what that looks like. But Harper always tees off against fastballs. If you look at the postseason as a whole, what's much more interesting is what Harper is doing against sliders.

Sliders were what Harper struggled the most against all season -- both regular sliders (higher velocity, tighter break) and the trendy "sweeper" style of slider (slower, more horizontal movement). Against sliders and sweepers during the regular season, Harper batted just .224 and slugged .388, with a 31% strikeout rate.

But in the playoffs? Harper is hammering those same sliders and sweepers.

Harper vs. sliders/sweepers in 2023
Reg. season: .224 BA (26-for-116) / .388 SLG, 4 HR, 39 K, 11 BB
Postseason: .500 BA (6-for-12) / 1.250 SLG, 3 HR, 2 K, 2 BB

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Harper leads the 2023 postseason in hits against sliders and sweepers, and he's tied for the most home runs with the D-backs' Gabriel Moreno.

Half of Harper's 12 postseason hits this year and three of his five home runs are against sliders and sweepers. He has more homers off sliders and sweepers in the playoffs than he does strikeouts. He's nearly equaled his home run total against those pitch types from the regular season. So much for that being a weakness.

Most of the damage Harper's done so far came in the first two rounds of the playoffs. The Marlins and Braves tried to attack Harper with those two slider varieties, and Harper made them pay.

Nearly half the pitches Harper saw in the Wild Card Series and Division Series were sliders or sweepers, more than double the rate he saw those two pitch types in the regular season. And Harper punished Miami and Atlanta.

Braves ace Spencer Strider, for example, had arguably the most dominant slider in baseball in 2023. He racked up 139 strikeouts on sliders during the regular season, the most K's by any pitcher on any individual pitch type, and allowed only four home runs on the 1,042 sliders he threw.

When he faced Harper in the playoffs, Harper crushed a 115.3 mph home run off Strider's slider -- the hardest-hit ball Strider has allowed in his MLB career, and one of the hardest home runs hit against a slider in the postseason under Statcast tracking (since 2015).

Now, in the NLCS, the D-backs have stopped trying to go after Harper in that way. He's barely seen sliders -- about one in every 10 pitches against Arizona.

The D-backs are a much less slider-heavy pitching staff to begin with … but they also had to see what Harper did to sliders against his opponents before them.

Slider/sweeper usage vs. Harper in 2023
Regular season -- 22%
Wild Card/Division Series -- 45%
NLCS -- 12%

But that just means Harper has pivoted back to hammering heaters for a series. And he's still ready for the sliders when they come.

When he faced D-backs closer Paul Sewald, a big sweeper user, in the ninth inning of Game 3, Harper drew a walk against the sweeper. In Game 1, he also ripped a 112 mph RBI single off Gallen's cutter, which functions like a hard slider for Arizona's ace (Gallen rarely throws a true slider).

If the Phillies advance to the World Series, keep Harper's turnaround against sliders in mind. The Astros and Rangers -- especially the Astros -- have key pitchers whose sliders and sweepers are important weapons. That includes starters like Houston's Justin Verlander and Cristian Javier and Texas' Max Scherzer (Scherzer uses a cutter against left-handed hitters like Harper to do the same job of a slider), plus the late-inning bullpen arms for both teams.

Interestingly, what Harper is doing this postseason is the opposite of what happened during the Phillies' 2022 pennant run. Last year, Harper raked against sliders in the regular season, but in the playoffs, the pitch was one of the only ways to get him out.

Harper vs. sliders/sweepers in 2022
Reg. season: .311 BA / .492 SLG
Postseason: .125 BA / .125 SLG

The Phillies superstar would certainly rather have it the way things are going right now: Dangerous against any pitch type in the games that matter most.