SAN FRANCISCO -- Kole Calhoun rounded second base and headed for third. Halfway between the bases, his running stride suddenly shifted. He wasn’t OK. He was hurt.

With the play still active, Calhoun willed his body to third base, sliding head first. While on his stomach, Calhoun, who knew very well that his body was damaged, curled his hand into a fist and slammed it on the base. A trainer came out to look at him, but there was no discussion to be had. The 33-year-old’s facial expression and body language said it all. He was coming out of this game.

Calhoun’s initial diagnosis, which was announced in the middle of the D-backs’ 7-2 loss to the Giants on Wednesday at Oracle Park, was a strained left hamstring. It was the same muscle that Calhoun had undergone surgery on in late April, causing him to miss more than two months.

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The severity of the injury is not yet known and additional tests will be conducted. Regardless, this much is certain: The typically durable outfielder has suffered another setback, one that threatens to compromise any plan of salvaging an already frustrating season.

“It’s heartbreaking,” said manager Torey Lovullo. “I didn’t know what to say to him today. I just saw the discomfort he was in. I saw the frustration on his face. I just tried to align with him and just tell him, ‘Man, I’m sorry you’re having to go through this.’

“I feel for him. I’m the manager of this baseball team and it’s my responsibility to keep players healthy and make sure they’re in a good spot each and every day. I hurt. I hurt badly for him. He’s such a good teammate. I know his teammates are feeling the same way, as well.”

The injury came as a surprise to Calhoun, who said that his hamstring was actually feeling pretty good and that he'd had more strength since returning in early July from the injured list. Calhoun pointed out that while this injury is to the same leg, it occurred in a different spot.

Regardless of how much time Calhoun misses, this is the latest in a series of ailments that Calhoun has dealt with in a year best described as brutal.

Calhoun, who played in 91.2 percent of his team’s games from 2014 to 2020, began 2021 on the injured list after undergoing surgery on his right knee for a medial meniscus tear in early March. It was his first time missing Opening Day since becoming an everyday player.

The outfielder returned on April 9, but only got a handful of games under his belt before sustaining a left hamstring strain. It was severe enough to warrant Calhoun going under the knife. The surgery and subsequent recovery caused Calhoun to miss more than two months. From the perspective of availability, this season would be his shortest.

Over the last half-decade, few players have been penciled into the lineup as much as Calhoun. From 2014 to 2020, Calhoun ranked 13th in games played. This season, Calhoun has been limited to 36 of the D-backs’ 115 games, and how many more he plays becomes the burning question.

“It’s been a heck of a year, man,” Calhoun said. “It’s a knee and the hamstring and getting a chance to come back. I don’t know. Start feeling kind of good, something pops up. It’s a roller coaster of emotions. Like I said, it is what it is. I can’t change it.”

Calhoun was very cognizant of the element of time as he discussed his injury.

The outfielder acknowledged the recovery time needed for hamstring injuries, saying it's seldom the allotted 10 days on the injured list. He also addressed the fact that the season’s final days are fast approaching. If the prognosis is poor, Wednesday night could be Calhoun’s last game of the season.

There’s also a scenario where this five-run loss could also be his last game with Arizona as Calhoun’s two-year deal is set to expire after this season. By signing with the D-backs prior to the 2020 season, Calhoun, who grew up in Buckeye, Ariz., had an opportunity to come home.

“I don’t know,” Calhoun said when asked about whether this could be his final game. “We’ll see what happens. Never know what the future holds, but we’ll see. That’s out of my control. I’ll let the team decide.”