It didn’t take long for the Giants’ bats to get rolling Tuesday in a doubleheader against the Rockies at Coors Field. 

Brandon Belt launched a grand slam and Buster Posey added a solo shot as the Giants erupted for 10 runs in the first inning to cruise to a 12-4 win in the seven-inning first game. It marked the first time the Giants have scored 10 runs in the first inning since June 29, 1967, against the Cardinals, when they scored 11 in the first -- nine of them against Hall of Famer Bob Gibson.

• Box score

“The one thing we know about Coors Fields is there isn’t really a lead that feels safe,” manager Gabe Kapler said. “We were just talking about how you’re up six runs, eight runs, 10 runs, and you feel like at any moment, the momentum of the game can shift. We saw that, even in the seven-inning game today. It was nice to have that cushion, but I don’t think at any point did we feel comfortable taking our foot off the gas.”

The Giants sent 13 batters to the plate in the nearly 30-minute first inning, collecting two homers, two doubles, four singles and two walks.

Rockies right-hander Germán Márquez allowed the first six batters he faced to reach base and departed after recording only two outs and throwing 36 pitches. Márquez left three runners on base and exited with the Rockies trailing, 5-0.

The Giants continued to pile on against reliever Jhoulys Chacín, who misplaced a 3-2 fastball that Belt drove out to right-center field for his third career grand slam. Belt’s fifth home run of the year traveled an estimated 452 feet, his fourth-longest homer since Statcast tracking began in 2015.

Belt also opened the scoring by delivering an RBI single off Márquez in his first at-bat in the inning. His five RBIs were the most by a Giants player in a single inning since Juan Uribe drove in six runs in the second inning on Sept. 23, 2010, against the Cubs.

Posey capped the 10 spot with his seventh home run of the year, a solo shot out to right field. Through his first 19 games of the year, Posey has matched his home run total from 2019, when he posted a career-low .688 OPS in his first season back from right hip surgery. Posey did not play in ‘20.

“I think the power is coming from health, first and foremost,” Kapler said. “Some time down to allow his body to heal. I think there have been some mechanical adjustments that are showing up. He did a lot of work this offseason on his swing, so the balls that he’s hitting his hardest right now are in the air. He’s clearly using the whole field. That’s one thing that’s really standing out, it’s line to line for him. When he’s hitting the ball to the opposite field, it’s with authority and it’s carrying.

“Finally, I think his confidence is really coming through. I think he feels healthy and strong in the batter’s box. It’s allowing him to ask his body to do things, and his body is responding.”

Raimel Tapia breathed some life into the Rockies by hammering a grand slam off right-hander Aaron Sanchez that cut the Giants’ lead to 10-4 in the fourth inning, but Brandon Crawford later added some extra cushion for the Giants with a two-run shot in the sixth.

Crawford, who returned to the starting lineup for the first time since he suffered a left calf bruise on Friday, golfed an 0-2 slider from lefty reliever Lucas Gilbreath out to the Rockies’ bullpen in right-center field for his fifth home run of the year. With 576 RBIs, Crawford surpassed Rich Aurilia for sole possession of 10th place on the all-time RBI list in the San Francisco era.

“We’ve got a savvy group,” Sanchez said. “We’ve been around for a while. Some taste of playoff experience and some winning baseball, so for me, I feel like that’s a great combination to have going into the year and for the rest of the year.”