J.D. Martinez (left) of the Boston Red Sox is congratulated by Rafael Devers after he hit a grand slam home run against the Houston Astros in the first inning of Game Two of the American League Championship Series at Minute Maid Park on October 16, 2021 in Houston, Texas. (Photo by Carmen Mandato / GETTY IMAGES NORTH AMERICA / Getty Images via AFP)

J.D. Martinez and Rafael Devers delivered a historic brace of grand slams Saturday to propel the Boston Red Sox to a 9-5 victory over the Houston Astros, evening their American League Championship Series at one game apiece.

Designated hitter Martinez came to the plate with two outs and the bases loaded in the first inning and launched a 1-0 fastball from Astros starting pitcher Luis Garcia 363 feet into the right-field stands to give the Red Sox a fast 4-0 lead in Houston.

It was the second home run of the 2021 post-season for Martinez, who missed the first two games of Boston’s playoff run with a sprained ankle.

Stunningly, the Red Sox — who fell 5-4 in a back-and-forth game-one battle on Friday — doubled their lead in the second inning.

Garcia walked Kevin Plawecki to open the inning, then departed with right-knee discomfort.

His replacement, Jake Odorizzi, gave up singles to Christian Arroyo and Enrique Hernandez to load the bases and Devers hit a 357-foot drive up the right-field line that cleared the wall just inside of the foul pole for another grand slam.

It made Boston the first team in post-season history to hit two grand slams in one game.

“That was the first one? That’s interesting,” Martinez said, adding that he felt that in the at-bat the pressure was all on Garcia.

“It’s the first inning. He has bases loaded. I’m trying to tell myself that, trying to stay relaxed and just looking for a pitch so I can just put a barrel on it,” Martinez said. “Just trying to see something deep and just put a good swing on it really.”

Hernandez, the hottest hitter in these playoffs with 16 hits, five homers and four doubles, added a solo homer in the fourth inning to put the Red Sox up 9-0.

Houston finally got on the board with two outs in the fourth on Kyle Tucker’s two-out, run-scoring double.

Yuli Gurriel added a single to right field that scored two more runs to make it 9-3 through four innings.

Gurriel and Jason Castro added solo homers in the ninth off Red Sox relief pitcher Darwinzon Hernandez before Ryan Brasier came in and retired Jose Altuve for the final out.

The Red Sox, back in the playoffs for the first time since they won the 2018 World Series, will try to ride the momentum when they host game three of the best-of-seven series on Monday.

Braves in walk-off

“It feels good,” Devers said of going back to Boston with a split of the first two games. 

“Houston is a really good team, and being able to split here and then now we’re able to go back home to Fenway where we’re comfortable and we know how we can play over there is really good for us.”

Atlanta third baseman Austin Riley was the hero in the Braves’ 3-2 victory over the Los Angeles Dodgers to open the National League Championship Series.

Riley cracked a walk-off single that scored second baseman Ozzie Albies from second base to break a 2-2 tie that had stood since the fourth inning and give the Braves the upper hand over the reigning World Series champions.

Albies had singled with one out then stole second base to set the stage for Riley — whose solo homer in the bottom of the fourth inning had forged the tie, answering a home run from Dodgers catcher Will Smith in the top of the inning.

“Base-hit, that’s all you need,” Riley said of his mindset in the decisive at-bat. “Put something in play and see what happens.”

As chants of “M-V-P” rained down on him, Riley called it “unbelievable.”

“It took a whole team effort,” he said. “Our pitching staff, you know they’ve been unbelievable. What they did was just amazing.”

Braves starting pitcher Max Fried allowed two runs in six innings, striking out five as he kept the Dodgers 1-for-5 with runners in scoring position.

Game two is on Sunday in Atlanta.