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Here's why Alonso could be the next great slugger

Rookie is applying Judge, Stanton-level power to balls in the air
@mattkellyMLB
April 15, 2019

When Pete Alonso laid into a Jonny Venters fastball and launched a 118.3 mph homer last Thursday, he did more than crush the hardest-hit dinger of the season. He also gained access to an extremely exclusive club. Alonso’s laser beam not only set a Mets record for homers tracked by

When Pete Alonso laid into a Jonny Venters fastball and launched a 118.3 mph homer last Thursday, he did more than crush the hardest-hit dinger of the season. He also gained access to an extremely exclusive club.

Alonso’s laser beam not only set a Mets record for homers tracked by Statcast since 2015; it tied for the ninth-hardest homer hit by any player in that span. Yankees sluggers Aaron Judge and Giancarlo Stanton have dominated that category ever since Judge burst onto the scene two years ago, but Alonso is now the first hitter to break their stranglehold on the top 10.

Hardest-hit HRs in MLB since 2015
1. Giancarlo Stanton, Yankees: 121.7 mph, 8/9/18
2. Aaron Judge, Yankees: 121.0 mph, 6/10/17
3-T. Stanton: 119.3 mph, 6/6/18
3-T. Judge: 119.3 mph, 4/28/17
5. Stanton: 119.2 mph, 6/23/15
6-T. Stanton: 118.6 mph, 9/28/17
6-T. Judge: 118.6 mph, 6/11/17
8. Stanton: 118.5 mph, 4/23/15
9-T. Pete Alonso, Mets: 118.3 mph, 4/11/19
9-T. Judge: 118.3 mph, 9/30/17
9-T. Judge: 118.3 mph, 7/4/17

Only 14 players have hit a ball at least 118 mph since Statcast began tracking, but Alonso is now one of just three to hit one high and far enough to clear the fence. And that’s what might be the most exciting part of Alonso’s incredible start (.345/.419/.800, 6 HR and 17 RBIs). Hitting the ball as hard as Alonso does is a raw skill, and he’s at the very top percentile of the scale. But Alonso is pairing that raw power with launch to do the very best thing a hitter can do …

He’s hitting the ball extremely hard, and he’s hitting it in the air

Let’s start with barrels, the very best type of contact with combinations of exit velocity and launch angle that often yield extra-base hits. Alonso has struck 11 of them, tied for the most in baseball, and he’s also within MLB’s top five in barrel-per-batted ball rate. But Alonso’s contact has been productive even when he hasn’t barreled up pitches:

Highest fly ball + line drive rate, NL hitters, 2019
Min. 25 batted balls
1. Franmil Reyes, Padres: 69.4%
2. Cody Bellinger, Dodgers: 68.4%
3-T. Alonso: 66.7%
3-T. Michael Conforto, Mets: 66.7%
5. Melky Cabrera, Pirates: 64.9%

The term “launch angle” has become so synonymous with baseball's home run surge in recent years that it’s easy to think that Alonso is swinging for the fences every time. But pop-ups are nearly as ineffective as strikeouts, and a line drive that barely gets off the ground can be caught by an infielder (like when Tim Anderson robbed Judge on a 111.2 mph liner Saturday). The best “launch angle” balls clear those infielders but also don’t go straight up in the air, and there’s a happy medium measured by Statcast’s sweet-spot metric for liners and flies hit between eight and 32 degrees. MLB hitters combined to hit .594 and slug 1.099 on sweet-spot batted balls in 2018, and Alonso is right near the top in that regard, too.

Highest sweet-spot rate, NL hitters, 2019
Min. 25 batted balls
1. Bellinger: 52.6%
2. Anthony Rendon, Nationals: 52.1%
3. Curtis Granderson, Marlins: 51.9%
4. Adam Frazier, Pirates: 51.1%
5. Alonso: 50%

Alonso has averaged a 98.5 mph exit velocity on his sweet-spot contact, helping him go 14-for-18 (.778) with four homers and six doubles on those balls in play. His sweet-spot rate will almost surely cool off as the season progresses, as will the rest of those leaders, but it’s worth noting that Judge’s rate has topped out at 38.2% and Stanton at 31.6% -- both in 2017, when they combined to hit 111 homers. It’s hard for the Judges, Stantons and now, Alonsos, of the world to consistently lift 110-plus mph contact (MLB hitters have averaged a 10-degree launch angle on those balls since 2015), so if Alonso can settle his air ball rates somewhere around Judge and Stanton’s rates from two years ago, he could be in line for a very big year.

It’s extremely early, of course, and Alonso is sporting an above-average swing-and-miss rate just like Judge and Stanton. But Alonso is proving to be more than a fastball hunter so far, holding his own against both breaking balls (.333 BA, .667 SLG) and changeups and splitters (.273 BA, .545 SLG). He’s hit just five of his 18 batted balls against secondary pitches into the ground, and he’s hit those pitches as hard as anyone.

Highest avg. exit velocity against secondary pitches
Min. 10 batted balls
1. Judge: 97.8 mph
2. Alonso: 97.0 mph
3. Freddy Galvis, Blue Jays: 96.1 mph
4. J.D. Davis, Mets: 96.0 mph
5. Bellinger: 95.5 mph
Secondary pitches: All pitches besides four-seamers/two-seamers and sinkers/cutters

National League pitching coaches are formulating their adjustments for Alonso, and he’ll have to adjust back like any rookie does. But after two weeks, it’s clear many of the most important hitting tools are already there for the Mets’ new star.

Matt Kelly is a reporter for MLB.com based in New York. Follow him on Twitter at @mattkellyMLB.