What’s Gotten Into Geraldo Perdomo?

When the Diamondbacks signed Geraldo Perdomo to a four-year contract extension this past offseason, I understood why they wanted to keep him around. In a sport with plenty of jerks and grouches and tough hangs, Perdomo’s teammates say he’s a delight to be around. He’s Mr. “Say Hi to the Wife and Kids,” even if he’s not very good at finding your wife and kids in the stands.

But in terms of on-field production, I had my doubts. Perdomo was an average hitter in 2023 and 2024, and a competent defensive shortstop. He’d take a walk, but he wouldn’t hit for much power. He’s a terrific bunter, but if bunting is this high on a list of a player’s positive attributes, you start to worry he can’t do much else with his bat. Is a steady two-win player really the guy the Diamondbacks needed to lock up, with Zac Gallen and Merrill Kelly and Josh Naylor all in contract years? Especially with Jordan Lawlar on the verge of major league regular status?

What a fool I was to doubt Perdomo. He’s hitting .306/.402/.488 through 49 games. He’s already set a new career high in WAR (2.8, fifth among all position players) and tied his previous career high in home runs with six. Perdomo is also walking more than he strikes out; he’s perfect in 11 stolen base attempts, and his quality of contact is through the roof.

So what the heck has gotten into Geraldo Perdomo?

Perdomo has always had good contact skills and good plate discipline, but he’s also one of those switch-hitters who’s completely different depending on which side of the plate he’s hitting from:

From the left side, he’s always put the ball in the air and taken more of a power approach. From the right side, it’s more ground-and-pound. This year, he’s slashed his groundball rate and — best of all — replaced almost all of those grounders with line drives. If a hitter increases his line drive rate from 18% to 28%, one should not be surprised if his wRC+ also goes up 50 points or so.

Perdomo is also swinging the bat harder, especially from the right side, where his average bat speed has gone from 67.4 mph to 69.4 mph year-on-year, and his fast swing rate (the percentage of swings at 75 mph or more) has risen from 1.5% to 13.9%.

Perdomo’s not exactly Joey Gallo, but at 6-foot-2, 203 pounds, he’s a big, strong dude. A guy like that swinging the bat harder should obviously lead to an offensive surge, especially if his already-elite strike zone judgement and contact skills remain unaffected.

So here’s the thing. While Perdomo’s right-side swing attributes look great compared to what he was doing last year, he still doesn’t hit the ball hard at all:

Perdomo’s hard-hit rate is in the 18th percentile this year. His bat speed is in the eighth percentile. This is still in the Punch-and-Judy neighborhood.

So how is he so good?

For starters, it helps when you walk 14.7% of the time and strike out just 11.8% of the time. Perdomo is extremely selective. Out of 164 qualified hitters this year, he has the seventh-lowest overall swing rate, one spot ahead of Kyle Schwarber. His chase rate is the third lowest in baseball. He’s also top 10 in the league in both in-zone and overall contact rate.

At the same time, his out-of-zone contact rate is only 65.7%, or 33rd highest. Which is, paradoxically, better for him. Unless you’re Luis Arraez, who’s making contact on 95.1% of swings outside the zone this year, and somehow hitting .404 on those swings, you’re not going to end up doing much with contact outside the zone anyway.

Basically, this year Perdomo is what it’d look like if Juan Soto never went to the gym. He’s an extreme strike miser, meaning he hardly ever chases pitches outside the zone, and he hardly ever gives away strikes by missing pitches he swings at.

These seem like the two attributes you’d most want from a hitter, right? So you’d expect a list of strike misers to just be a list of great hitters. Let’s see. Perdomo is one of only eight hitters who’s in the 90th percentile or better this year for both whiff rate and chase rate. Here they are:

Turns out these qualities are extremely correlated with being named Alex, but less so with being a great hitter. Obviously, seven of the eight names here are running wRC+ marks over 100, but a lot of these guys were not good last year. Urías, for instance, is currently hitting .266 after failing to hit .200 in either of the past two seasons. Frelick, Meidroth, and Friedl are weird hitters more than anything else.

What they have in common is low bat speed. Just like Perdomo.

Perdomo makes me question that article of faith about how the hardest thing to do in sports is to hit a round ball with a round bat. I suppose it’s not actually all that hard. The trick is to hit the round ball with the round bat in just the right spot, while swinging the bat as fast as possible. It’s very, very difficult to do.

For most guys, it’s a tradeoff between bat speed and bat control. The grid at the top of Baseball Savant’s bat tracking leaderboard actually illustrates that bargain quite well. You can see who’s ripping the bat through the zone at maximum speed (Oneil Cruz, Aaron Judge), and who’s swinging the bat more slowly in order to place the ball perfectly on the sweet spot (Arraez, Jacob Wilson, Mookie Betts).

If you go to Perdomo’s Baseball Savant page and look at the summary section, you’ll see that there is one quality-of-contact metric in which he is not only up from last year, but above-average compared to the league: launch angle sweet spot percentage. This is the percentage of batted balls that come off the bat at a launch angle between eight and 32 degrees.

Perdomo’s sweet spot rate, 37.0%, is a career high, and an improvement of 8.1 percentage points from last season. But it’s not exactly uncharted territory for him. In 2023, Perdomo had a sweet spot rate of 35.4%, and his wRC+ was 98, not 145. His underlying numbers (including a .275 xwOBA) were even worse. The difference is that Perdomo has far below-average bat speed now, but in 2023, his bat speed was absolute rock-bottom, just 65.7 mph. Apparently, that’s slow enough that it doesn’t matter that much if you square the ball up.

This year, Perdomo is hitting the ball just hard enough to get his money’s worth out of that solid contact. Add in the fact that his strikeout and walk numbers went from excellent to extraordinary, and that’s good enough to turn an average hitter with no power into a well-rounded offensive player and elite on-base guy.

For what it’s worth, the Diamondbacks as a team pop off the bat tracking leaderboard. They’re first in the league in squared up rate (which measures the percentage of potential exit velo that gets transferred to the ball on contact), and second to the Yankees in ideal attack angle percentage. Corbin Carroll and Ketel Marte have been elite at combining bat speed with a productive swing angle, but a bunch of Diamondbacks hitters — Perdomo, Lourdes Gurriel Jr., Gabriel Moreno, and even Alek Thomas — are hitting the sweet spot regularly.

The last time the Diamondbacks went to the playoffs, Perdomo hit at the bottom of the order and made his greatest impact by bunting: five sacrifices and a bunt single in 17 games. If Arizona gets back there this October, he’ll be higher in the order, and much less willing to give away outs.