BALTIMORE -- A’s manager Mark Kotsay called it “pick your poison.”

Option One: Face Adley Rutschman -- the red-hot Orioles slugger who recently became one of two players in franchise history with a pair of four-plus-hit performances within the team’s first nine games of a season -- with runners on second and third and two outs in the seventh inning.

Option Two: Intentionally walk Rutschman and face Ryan Mountcastle with the bases loaded, a right-on-right matchup for reliever Dany Jiménez. But here’s the catch -- Mountcastle has been heating up himself, having already homered and driven in five runs on the night.

Kotsay went the latter route. Perhaps both would have gone in Baltimore’s favor. But this one did so in historic fashion.

Mountcastle jolted a grand slam to put Tuesday’s game out of reach and seal the Orioles’ 12-8 victory at Camden Yards. His nine RBIs matched the single-game franchise record held by Baseball Hall of Famer Eddie Murray (Aug. 26, 1985) and Jim Gentile (May 9, 1961).

“Two greats,” Mountcastle said. “To tie them in, I guess, any category is super special, pretty cool.”

There have been only 42 instances of a player driving in nine or more RBIs in a game in AL/NL history. The most recent had been Adam Duvall, who achieved the feat with the Braves vs. the Marlins on Sept. 9, 2020. The AL/NL record for RBIs in a game is 12, both for the Cardinals (Jim Bottomley on Sept. 16, 1924, and Mark Whiten on Sept. 7, 1993).

Mountcastle’s slam traveled a Statcast-projected 456 feet (the longest of his 65 career homers) and left his bat at 111 mph.

When the seventh inning ended and it was time for the Orioles to take the field for the eighth, everybody waited back. The team allowed Mountcastle to run out to first base alone and soak in the loud ovation from the fans.

Mountcastle hadn’t even realized the magnitude of his accomplishment until assistant pitching coach Darren Holmes had mentioned it.

“I never knew until Holmesy let me know,” Mountcastle said. “He was like, ‘Did you know you have nine RBIs?’ I was like, ‘I had no clue.’ And I was like, ‘That’s a lot, man.’”

It was a rewarding night for Mountcastle, who has had some trouble clearing Camden’s high left-field wall that was pushed back prior to the 2022 season. Per Baseball Savant, the 26-year-old ranks among baseball’s best this year in barrel rate (97th percentile), average exit velocity (95th) and hard-hit percentage (91st).

Yet, Mountcastle had only two homers through nine games. He spent much of the Orioles’ first home series vs. the Yankees this past weekend swatting balls to deep left field -- just not deep enough.

That wasn’t an issue Tuesday. Before the massive slam, Mountcastle belted a 417-foot three-run homer to left in the fifth that cut the A’s lead to 7-6 and got the O’s back in the game.

“He’s just getting good pitches to hit and putting barrels on them,” said fellow right-handed hitter Austin Hays, who has also hit a homer each of the past two nights. “He’s got big-time power where he can hit a homer to any field on any pitch in any part of the zone.”

Mountcastle is slashing .289/.320/.711 with five home runs (tied for the most in the Majors) and an MLB-high 18 RBIs. The only previous Baltimore player to have that many homers and RBIs through the team’s first 11 games of a season was Chris Davis, who had six homers and 19 RBIs at that point in 2013. He finished with a franchise-record 53 home runs and 138 RBIs.

Brandon Hyde hasn’t been surprised by Mountcastle’s recent offensive prowess. The Orioles’ manager had been impressed with the slugger’s offensive approach in Spring Training and believes he’s developing into a “much mature hitter” in his fourth big league season.

“The power he has is incredible,” Hyde said. “He’s got great bat-to-ball skills with balls in the strike zone or just off, and you make a mistake and he’s ready to hit. He’s off to a great start this year. Love the confidence he’s playing with right now.”

It helps that opposing teams can’t pitch around Mountcastle at this point. There are too many other talented hitters in Baltimore’s lineup, including Rutschman (slashing .395/.490/.628 with three homers) and Hays (.333/.366/.692 and three homers).

If a team opts to face Mountcastle, he has the ability to make them pay, which he showed Tuesday in a big way.

“Our offense, our lineup top to bottom, is scary when we’re rolling,” Mountcastle said. “Hopefully, we can keep it going.”