The Giants capped the Fourth of July weekend with a 5-2 win over the D-backs that clinched a series victory at Chase Field on Sunday night, but the celebration was dampened after catcher Buster Posey was forced to exit the game with a left thumb injury.

Posey immediately threw off his glove and grimaced in pain after being struck by a foul tip from pinch-hitter Daulton Varsho on the thumb area of his left hand in the bottom of the sixth inning. Posey took two warmup throws and tried to stay in the game following a quick evaluation from head athletic trainer Dave Groeschner and manager Gabe Kapler, but he caught only one more pitch from right-hander Anthony DeSclafani -- a third strike to Varsho -- before taking himself out of the game.

X-rays came back negative on Posey, who was diagnosed with a left thumb contusion. Kapler said Posey isn’t expected to start against the Cardinals on Monday afternoon at Oracle Park, but he didn’t rule out the possibility that Posey could be available off the bench as the Giants kick off their final homestand before the All-Star break.

“You see me smiling, that’s my level of relief,” Kapler said. “My level of concern when Buster threw his glove off was pretty high, obviously. He’s pretty even and doesn’t react with that much emotion very often, so obviously, we take that really seriously. We went out there and gave him a chance to stay in the game. He’s always going to fight for that, but we thought it was best to get him out of there and get him checked out. Obviously, it’s good news on the X-rays. We’ll try to get him ready for tomorrow’s baseball game.”

Backup Curt Casali entered the game to replace Posey, who has been one of the Giants’ most indispensable players this year. Posey, who was selected to start behind the plate for the National League at the 2021 All-Star Game at Coors Field on July 13, entered Sunday batting .327 with a .965 OPS and 12 home runs over 57 games this season.

The 34-year-old veteran had enjoyed another productive night against the D-backs before his premature exit, putting the Giants on the board with an RBI single off left-hander Caleb Smith in the first inning and drawing a walk in his final plate appearance in the sixth.

“It’s really unfortunate,” DeSclafani said. “It’s definitely alarming. He’s obviously a big reason for us being successful. I don’t know any of the details, but hopefully it’s nothing serious, and he’s back soon.”

Posey’s injury deflected some attention away from another brilliant outing from DeSclafani, who came within one out of securing his third complete game of the year. DeSclafani gave up two runs on six hits over 8 2/3 innings to improve to 9-3 with a 2.84 ERA over 17 starts this year.

His strong body of work could make him a candidate to join Posey, Brandon Crawford and Kevin Gausman at the Midsummer Classic, as more players are expected to be added to the NL squad as replacements this week. Still, the competition for the final spots will be tough, as talented NL starters like Max Scherzer, Walker Buehler, Freddy Peralta and Taijuan Walker also figure to be in the mix.

“I think I’ve had a pretty good first half so far,” DeSclafani said. “It’s great to even be considered. Obviously, I would love to join and get to experience everything. With that being said, there are a lot of guys having really good seasons and a lot of guys that are deserving. If I was to be one of them, it’d be awesome. But I know the reality of it and the chance that it might not happen. At the end of the day, I’ve just got to continue to get better. More than anything, I’m excited to keep winning on this ballclub.”

The D-backs ended the night with a fireworks spectacular at Chase Field, but platoon bats Austin Slater and Darin Ruf supplied their own pyrotechnics at the plate after launching long home runs off Smith to pace the Giants’ offense. Slater delivered a mammoth blast off an Arizona lefty for the second consecutive night, as he extended the Giants’ lead to 3-0 with a 467-foot solo shot in the third. It was the longest home run Slater has hit since Statcast began tracking in 2015, topping the 463-foot moonshot he belted off Ryan Buchter on Saturday.

Ruf later added more cushion with his seventh homer of the year, a two-run shot that landed halfway up the left-field bleachers in the sixth.

“We joke with each other, we’re Team Righty waiting for a left-handed pitcher,” Slater said. “We understand the role. We understand how we play baseball on this team and how we match up. When you go through a stretch of not getting hits, especially in limited opportunities, you feel like you’re letting the guys down, so it always feels great to come up in these kinds of situations and win these kinds of games.”

After taking three of four games from the last-place D-backs, the Giants (53-30) retained their perch atop the National League West and stayed a half-game ahead of the red-hot Dodgers, who extended their winning streak to nine games after finishing off a four-game sweep of the Nationals on Sunday.