OAKLAND -- In his first taste of big league action with the Marlins last season, JJ Bleday struggled to deal with the pressure of living up to his status as a top prospect. The result: A disappointing .167/.277/.309 slash line in 65 games with Miami.

Traded to the A’s in exchange for left-hander A.J. Puk this offseason, Bleday took the lessons learned from his first experience in the Majors and formulated a plan to be better prepared for the next opportunity. Called up from Triple-A Las Vegas earlier this week, it didn’t take long for him to get comfortable in his new surroundings.

Playing in his second game with the A’s in Thursday’s 5-3 loss to the Mariners at the Coliseum, Bleday put together a two-hit effort that was highlighted by a booming solo shot to right off George Kirby, who entered the day having allowed just one home run through his first 30 2/3 innings pitched this season.

“Good aggressive swings,” manager Mark Kotsay said of Bleday. “You like to see that, a guy that feels comfortable coming in and swinging the bat looking to do damage. He [also] looked comfortable in right field. Good sign for that young man.”

It was the type of performance that was becoming a regular occurrence for Bleday in Triple-A and earned him a quick call to Oakland and insertion into the middle of the A’s lineup. Over 25 games with Las Vegas, the 25-year-old outfielder hit .316 with a 1.072 OPS, seven homers, seven doubles and 19 RBIs.

Bleday credited his hot start to an adjustment in his approach at the plate. It began shortly after finding out he was traded just before Spring Training on Feb. 11. Working out at his alma mater, Vanderbilt University, Bleday linked up with Orioles utility man Adam Frazier and discovered a new routine that involves hitting foam balls off a pitching machine. The exercise helps him stay more on top of fastballs and maintain a line-drive approach, something that evaded Bleday during his time with the Marlins in 2022.

“I had a lot of foul balls on heaters and certain pitches that I should be putting in play,” Bleday said. “You only get a certain amount every night in the big leagues, so you have to do your best to put those in play. … I started using these foam balls. We have them here with Oakland, and it’s like the most realistic, game-like heater you can get.”

Case in point: Thursday’s game. Bleday’s homer and single came off fastballs of 94 mph+ from Kirby. The homer was on a fastball high in the zone that was scorched 107.9 mph off the bat, which registered as the second-hardest exit velocity of the game from either team, according to Statcast.

“I remember I talked to Freddie Freeman when I got called up last year, and I’m like, ‘Hey Freddie, what’s your approach?’” Bleday said. “He was like, ‘I just try to hit a line drive over the shortstop’s head.’ I thought I’d try that. Eventually, those turn into home runs, as crazy as it sounds. Just let the velo do the thing and try to be accurate. I’m just trying to be accurate and put balls in play.”

Bleday, the fourth overall selection of the 2019 MLB Draft, will get his chance to translate that sky-high potential with regular playing time going forward. But the contributions from him and the rest of Oakland’s offense were not enough on a day which saw starting pitcher Drew Rucinski tagged for five runs in just 3 2/3 innings. The fourth was his unraveling. After retiring his first two batters in the inning, the right-hander proceeded to walk four batters and allow two hits in what became a four-run frame for Seattle.

Ironically enough, Rucinski’s rough outing was followed by a scoreless effort by a struggling A’s bullpen that had recorded a blown save in each of the previous four games after the starter had departed with a lead. Newcomers Rico Garcia, Austin Pruitt and Spencer Patton, whose contracts were selected from Triple-A earlier in the day, combined for three scoreless innings.

“We’ve played better baseball in all facets. We just haven’t played it all at once,” Kotsay said. “We’ve had games where the offense hits, and we’ve not pitched. We’ve had good starting pitching and no bullpen. Today, we didn’t get great starting pitching, but our bullpen gave us a chance to come back.”