Brent Rooker had a better view than maybe anyone of A's teammate Zack Gelof’s first Major League hit.

Rooker took his lead off second base during a July 14 game against the Twins in Oakland as Gelof -- the team's No. 3 prospect at the time of his promotion -- made contact on an 0-2 pitch in his second MLB at-bat.

“I just thought it was an average popup, and I went back to tag at second base,” Rooker recalled. “I only realized really late that he hit it really well and it was carrying.”

Despite being hit at a high launch angle of 42 degrees, the ball caromed off the very top of the wall in right-center field. Gelof had just missed his first career home run, but he still had a double. Rooker sprinted around third and scored with newfound admiration for his rookie teammate’s opposite-field power.

“That was pretty impressive,” Rooker said.

Rooker isn't the only one impressed by Gelof’s prowess at the plate in 2023. The rookie infielder -- the American League Rookie of the Month for August -- has cooled off since a record-setting start, but he’s still made himself a fixture in Oakland’s lineup and remains among the better young hitters in the league.

Here’s what makes Gelof stand out, how pitchers have begun to adjust to him and what he intends to do to stay hot at the plate.

All statistics are through Sunday's games.

Finding success early
Gelof, a second-round Draft pick out of Virginia in 2021, tore up Triple-A Las Vegas across 69 games in 2023: a .304 average, 12 homers, 21 doubles and 20 stolen bases.

But when he was called up to the Majors in mid-July, he could tell straightaway it was a whole new ballgame.

“I think the biggest thing is you can really feel the competition and just know that it’s real life, like work, and these are people’s careers, too,” Gelof said. “They’re going to do everything they can in their preparation to bring it every day no matter how you’re feeling.”

But Gelof proved himself capable of bringing it, too.

After the double to plate Rooker in his MLB debut, he legged out a triple in his second MLB game. Another double followed in game No. 3. Then the homers started coming.

Gelof first went deep on July 22 against the Astros, his eighth Major League game. He homered again on July 28, July 29, Aug. 1 and Aug. 3. 

After a two-homer performance against the Nationals on Aug. 13, Gelof went deep against the Royals on Aug. 21 to become the fastest A’s rookie to nine career homers (32 games).

At the end of that game, he was hitting .304 with a .994 OPS -- his highest postgame OPS since his third MLB game.

“It’s been awesome,” Gelof said of his early accomplishments. “Obviously, success is cool, and I’m ultimately just trying to win at this level.”

Excelling up and in
Of the 124 balls Gelof has put in play in 2023, not a single one has been classified as “weak” contact. His average exit velocity and barrel rate are both above average, and his 93rd-percentile sprint speed (a near-elite 29.2 feet per second) doesn’t hurt, either.

The 23-year-old is particularly adept at hitting high-and-inside pitches. On pitches in the top left corner of the strike zone (viewed from the catcher’s perspective), Gelof is 9-for-17 with three doubles and two homers. His .663 wOBA on pitches in that zone ranks third of 176 qualifying right-handed hitters, and his 1.059 slugging percentage ranks fifth in that group.

Gelof can use his quick hands to turn on an inside pitch for a homer -- or flick a ball the other way for a base hit.

While only 23 of Gelof’s batted balls (18.5%) have gone to the opposite field, his power in the other direction hasn’t gone unnoticed by his teammates.

“I think it’s rare for anybody,” Rooker said. “He hits balls in BP that way that I can’t hit like that. The ability to have as much power to the back side as you do to the inside is something pretty rare in this game, I think. It opens up a lot of doors for you offensively -- the ability to stay on pitches and know you don’t have to catch everything super far out front to hit for power.”

Handling the heat
Another big part of Gelof’s success? Absolutely crushing fastballs.

The rookie is slugging .630 against fastballs in 2023, the ninth-highest mark in the Majors (min. 75 PA). It’s good company to keep: The top five players on that list include Shohei Ohtani (No. 1), Aaron Judge (No. 2) and Corey Seager (No. 5).

Twenty-eight of Gelof’s 46 hits have come on fastballs, including eight of his 10 home runs. Seven of those homers came on four-seamers, on which Gelof’s .745 SLG ranks seventh in MLB.

Highest percentage of home runs coming on 4-seam fastballs, 2023
Min. 10 HR (206 hitters)
1-T. Zack Gelof (OAK): 70.0%
1-T. JJ Bleday (OAK): 70.0%
3-T. TJ Friedl (CIN): 66.7%
3-T. Joc Pederson (SF): 66.7%
5. Cedric Mullins (BAL): 61.5%

Consequently, it’s only natural that pitchers began to adjust to Gelof how one might expect: by throwing him fewer fastballs.

Through Aug. 13, the night of his two-home-run game in St. Louis, Gelof was seeing 54.3% fastballs, just below the league average of 55.1%. Since then, that percentage has dipped to 49.4%. It hasn’t gone unnoticed to Gelof, either.

“It’s probably less fastballs,” he said. “I think it’s just typical: sinkers in, sliders away, changeups down and then sneak the fastball in, too. I think that’s what all pitchers are trying to do, and it’s pretty tough, but there’s nothing to do but adjust.”

'Just get better'
It’s pretty much the core issue for any hitter enjoying a hot streak: How do you counter the adjustments pitchers will inevitably make?

Rooker is only in his fourth MLB season, but he’s a relative veteran in that regard. Not only did he have to deal with that in his rookie season in 2021 but again this year after a hot first half earned him an AL All-Star nod.

“You start getting different pitches, different locations,” Rooker said. “They pitch you differently in different counts. It happens quick. I don’t know what the exact sample size is they need to zero in on what they want to do, but it happens quicker than you think.”

As a rookie, that can be hard to deal with. Gelof isn’t immune: he’s hitting .247 with a .314 OBP and .403 SLG since Aug. 14 after posting a .281/.343/.635 slash line prior to that date.

The rookie said he’s glad he got his first taste of Major League action early enough in the year to be able to weather a relative cold spell.

“Going through the ups and downs, I think that’s the good thing about getting called up when I did: It’s enough time to go through a stretch of goods and bads and just keep adjusting and knowing what it takes for the next year,” Gelof said.

Asked how to make the adjustments he knows he’ll need to, Gelof mentioned working with teammates and coaches, staying disciplined and refraining from chasing pitches, particularly in hitters' counts.

The three most telling words in his answer?

"Just get better.”

It’s hardly that easy, but for a hitter like Gelof, it doesn’t seem out of the question.