First base was viewed as a position of depth for the Giants at the outset of the season, but their options have quickly dwindled following a rash of injuries to veterans Brandon Belt, Tommy La Stella, Wilmer Flores and Darin Ruf.

Ruf became the latest first baseman to hit the shelf, landing on the 10-day injured list with a right hamstring strain prior to the Giants’ series opener against the Dodgers on Thursday at Dodger Stadium.

Ruf, 34, sustained the injury after rounding first base in the sixth inning of San Francisco’s 5-4 win over the D-backs on Wednesday night at Chase Field. It was a brutal break for Ruf, who was slated to take over first-base duties after Belt was placed on the IL with a mild left oblique strain on Wednesday.

La Stella is currently on the 60-day IL and will be out until at least July, but Flores could return as early as Saturday. Like Ruf, La Stella and Flores are dealing with hamstring injuries.

• Giants' injury updates & roster moves

With their top four options at first base sidelined for now, the Giants will turn to rookie Jason Vosler and LaMonte Wade Jr, who was recalled from Triple-A Sacramento to replace Ruf on the 26-man roster on Thursday.

Vosler started at first base against left-hander David Price after crushing his first Major League home run to cap the Giants’ dramatic comeback on Wednesday, but manager Gabe Kapler said Wade could draw looks there as well.

Primarily an outfielder, Wade has made only six appearances at first base in the Majors, but he played first in college and took ground balls there during Spring Training.

“He hasn’t played first base in Sacramento, but he is prepared to play the position,” Kapler said. “We worked on it with him in Spring Training. Obviously, he’s plenty athletic to go over there. He’s going to do a little work today. We want to kind of open up the possibilities at first base, and LaMonte falls into that category as a guy that we can use to cover that position for us while Ruf is down.”

One name that isn’t being floated as an option at first base is Buster Posey, who has been playing two out of every three games and received a scheduled day off on Thursday. The Giants have been carefully monitoring Posey’s workload this season, and Kapler said he feels it’s in the club’s best interest to remain disciplined with the 34-year-old catcher’s usage to give him the best chance to stay healthy and fresh in 2021.

“We’re probably going to stay the course with Buster,” Kapler said. “I’m not saying it would be out of the question. It will always be on the table, and we’ll challenge our own positions on things regularly.”

Kazmir shifts to bullpen
With right-hander Logan Webb slated to return to the rotation on Saturday, Kapler said veteran left-hander Scott Kazmir will move to the bullpen and shift into more of a long relief role for the Giants. Kazmir, 37, will be available on Thursday after working four innings of one-run ball in his last start against the Dodgers on Saturday, which marked his first appearance in the Majors since 2016.