Fastballs aren't so trendy these days, but Spencer Strider doesn't seem to mind.

Fewer than half the pitches in MLB are fastballs for the first time in the 15 years of the pitch-tracking era. Fewer than one in three pitches are a four-seamer for the first time since 2010. Meanwhile, the Braves' 23-year-old rookie fireballer is throwing his fastball 70% of the time -- and blowing hitters away.

Of the 137 pitchers who've thrown at least 750 pitches this season, no one is throwing four-seamers more often than Strider, who has a 3.02 ERA and 13.2 strikeouts per nine innings entering his start Saturday. Even after moving from the bullpen to the starting rotation, Strider's big fastball remains Weapon No. 1.

As a reliever, Strider was throwing fastballs just under three quarters of the time, the second-highest four-seam usage of the 158 relievers who've thrown as many pitches as Strider out of the bullpen. As a starter, he's still throwing them two thirds of the time -- the highest fastball usage of the 157 starters who've thrown as many pitches as him in the rotation.

Why is Strider throwing so many heaters? Well … have you seen his fastball?

The 6-foot Strider generates triple-digit heat with his fastball with a delivery that's a mix of old school and new school -- a traditional drop-and-drive move to the plate coupled with the short arm action that's become popular with pitchers like Lucas Giolito and Shane Bieber. He's hit 100 mph or faster 43 times this season, 31 as a reliever and 13 as a starter. His four-seamer is averaging 98.2 mph (98.6 as a reliever, 97.9 as a starter), making it the second-hardest fastball among pitchers who've thrown a comparable amount, behind Hunter Greene.

Strider's fastball is his out pitch. He's racked up 52 K's on four-seamers, and 99 swings-and-misses, which are both top-five overall in the Majors … even though he spent the first two months of the season as a reliever.

Most K's on 4-seam fastballs, 2022
1. (tie) Gerrit Cole: 65
1. (tie) Tyler Mahle: 65
3. Carlos Rodón: 60
4. Spencer Strider: 52
5. Logan Gilbert: 50

It's no secret how Strider is coming after you: high heat. Strider pounds high-90s, rising fastballs at the top of the zone -- his four-seamer only drops 11 inches on its way to the plate, giving him two inches more "rise" than an average fastball -- and hitters don't catch up.

Thirty-two of those 52 four-seam strikeouts are elevated -- in the upper third of the strike zone or higher -- the fourth-most high-fastball K's of any pitcher. The average velo of Strider's fastball K's is 99.1 mph, with 10 in triple digits, including a 100.2 mph fastball to strike out Trea Turner to open his last start.

Most 100+ mph fastball K's, 2022
1. Jhoan Duran: 16
2. Ryan Helsley: 14
3. Hunter Greene: 13
4. (tie) Spencer Strider: 10
4. (tie) Emmanuel Clase: 10

Strider is one of only six pitchers averaging 99 mph or higher on their fastball when they strike you out. Greene (99.0) is the only other starter in that group, with the other pitchers being top relievers Jhoan Duran, Ryan Helsley, Edwin Díaz and Ryne Stanek. Only four other starters are averaging even 98-plus mph on their fastball K's: aces Sandy Alcantara (98.4), Gerrit Cole (98.4), Shohei Ohtani (98.1) and Shane McClanahan (98.0).

Strider's four-seamer almost makes you forget that he has a slider hitters are swinging and missing at 52% of the time (and a changeup that hitters are swinging and missing at 50% of the time, but he only throws that 5% of the time, mainly just to mix in against lefties). But that slider has such a high whiff rate because of how it plays off the fastball, which hitters have to first worry about catching up with at the top of the zone.

Both pitches come in true to the hitter -- Strider's four-seamer and slider only break horizontally about five inches, meaning the difference is mainly in the vertical drop. That creates some beautiful tunneling.

But it's the fastball half of the combo that's the key for Strider. Even with hitters whiffing on half their swings against the slider, Strider has more than double the K's on fastballs (52 to 23) and nearly double the swings-and-misses (99 to 53). Nearly three quarters of the outs Strider has recorded this season have been on four-seamers.

Highest % of outs recorded via 4-seam fastball, 2022
Min. 50 innings pitched
Spencer Strider: 72%
Mackenzie Gore: 68%
Cristian Javier: 68%
Joan Adon: 67%
Michael Kopech: 62%
Carlos Rodón: 61%

Sliders are in, but there's still nothing like the energy that comes from watching a power fastball explode past a hitter. Strider could ride his into becoming one of baseball's next wave of aces.