Catcher Chris Herrmann, who had arthroscopic knee surgery in March, said Tuesday afternoon that there were times early in his recovery when he experienced such discomfort that he wondered if it might signal the end of his career.

Instead, making his A’s debut Tuesday night, Herrmann, 31, announced his return with a bang.

Herrmann, activated from the injured list before the game, hit a grand slam in his second at-bat that helped lift the A’s to an 8-6 win over the Twins. The A’s said Herrmann is the first player in franchise history to record a grand slam in his first game with the team.

“It felt amazing,” Herrmann said. “It’s been a grind. I can’t thank my family enough for all of the support that I’ve had over the past three months. There were times when I didn’t even think I was going to be able to play this year and my teammates, coaching staff, everybody was behind my back all the time.”

Herrmann, 31, was pegged for a roster spot this spring before his surgery to repair cartilage. His recovery coincided with Josh Phegley seizing the everyday catcher role in Oakland. But out of options and with his rehab window up, Herrmann joined the A’s on Tuesday. It helped that he’d gone 11-for-23 over his last six games at Triple-A Las Vegas.

A’s manager Bob Melvin said he wanted to have Herrmann in the lineup immediately as he was “swinging the bat pretty good” at Triple-A. Herrmann struck out with two runners on in his first at-bat against starter Jake Odorizzi and said he “tried not to do too much” with the bases loaded in the fourth. The result was his second grand slam in the majors and first since 2013.

“Nice little impact,” Melvin said. “When you hit a home run period, let alone a grand slam, it makes you feel like you belong pretty quickly with the team. So, nice to get him off to a good start.”

Before the game, Melvin said catcher will “not necessarily” become a straight platoon between Herrmann, a left-handed hitter, and Phegley. Oakland sent catcher Beau Taylor back to Triple-A to clear a roster spot for Herrmann. “It’s not like we’re going to run from Phegs,” Melvin said in his pregame media session. “Phegs has been doing a great job this year.”

Herrmann’s was the loudest blast in a game that befit the two teams who entered Tuesday with the most home runs in the majors since May 13. The Twins got a two-run homer from Miguel Sano and two solo homers from catcher Jason Castro, a Castro Valley High and Stanford alum. The A’s also had a two-run homer by Matt Olson (in the third) and a solo shot from Mark Canha that provided breathing room in the late innings.

Olson’s homer was his 17th since May 12 — the most in the majors in that span. The A’s, who’ve won 11 of their past 14 games, improved to 9-1 against AL Central teams this season and are a season-high eight games over .500.

After throwing six shutout innings in his previous start at St. Louis, the A’s Daniel Mengden fell behind 3-0 in the third innng Tuesday. Melvin, though, credited Mengden with reaching the sixth, departing with two outs after Luis Arraez’s RBI double.

Mengden was “getting ahead, which is key for him,” Melvin said. “You get a few balls in the middle of the plate to this team, they’re going to make you pay for it. … But at the end of the day, he comes out with a lead and we get a win.”

Mengden had worked with Herrmann this spring and at Triple-A and said Tuesday “was a good outing between us, good game plan, good execution.” Herrmann, who also caught relievers Yusmeiro Petit, Joakim Soria and Liam Hendriks, said he relied heavily on Phegley and pitching coach Scott Emerson for insight between innings.

“It’s learning on the fly,” Melvin said, “so he did a really nice job.”

Herrmann batted eighth Tuesday ahead of Franklin Barreto, who started a second consecutive game at second base. Melvin said before the game that Barreto will be the regular second baseman for now with Jurickson Profar moving to a utility role. Barreto had a double in four at-bats and scored on Olson’s homer.

“Frankie’s going to probably get the majority of time at second,” Melvin said. “Not necessarily every day, but I think this is a great opportunity for him, for the first time in the big leagues, to get some consistent at-bats.”

Matt Kawahara is a San Francisco Chronicle staff writer. Email: mkawahara@sfchronicle.com Twitter: @matthewkawahara