SAN FRANCISCO -- Brandon Belt’s regular season is over. And he'll be missing the start of the postseason, too.

On Tuesday, Belt was placed on the 10-day injured list with a left thumb fracture (retroactive to Monday) by the Giants, who have a two-game lead in the National League West. Manager Gabe Kapler said after Tuesday's 6-4 win over the D-backs that Belt, who was struck with a fastball while attempting to bunt against the Rockies on Sunday, will be re-evaluated in a "couple weeks," a prognosis that likely rules out Belt for much of the postseason, if not all of it.

If San Francisco wins the division, its first postseason game would be Oct. 8. The NL Wild Card Game is slated for Oct. 6.

“It’s not optimal, but I think we’re going to be fine because our players are prepared for it," Giants manager Gabe Kapler said of the loss of Belt.

The loss of Belt, who ends the season with a career-high 29 home runs, cannot be overstated. When healthy, he has been one of the best first basemen in baseball. In recent weeks, he’s arguably been the best.

Upon returning from the injured list on Aug. 5 -- after missing two months with a right knee ailment -- Belt played some of the best baseball of his career. In his last 42 games, Belt slashed .297/.394/.690 with 18 home runs. During that stretch, he posted a wRC+ of 183, bested only by Washington's Juan Soto (217), Philadelphia's Bryce Harper (202) and St. Louis' Paul Goldschmidt (194).

Belt's absence could put a dent into San Francisco’s aspirations of a deep postseason run. The Giants may struggle to replicate his production and specific brand of jovial leadership. What they can do, however, is lean on their hallmark: depth.

San Francisco has no shortage of options to play first base. LaMonte Wade Jr., who started at first on Tuesday, is primarily an outfielder, but he has played 228 career innings (191 this season) at the position. Wilmer Flores has played 1,288 2/3 career innings at first base and will get his fair share of opportunities. There’s also Darin Ruf, who Kapler is optimistic will return on Thursday from a right oblique strain.

Along with those three, Kris Bryant, Tommy La Stella, Austin Slater, Buster Posey and Curt Casali have all spent some time at first base. It’s unlikely that Kapler turns to any of them -- especially Posey or Casali -- but he has a plethora of options at his disposal.

“We have a fun little mix-and-match group now between Wade and Flores, and Ruf is right around the corner,” Kapler said. “I think we’re going to be able to successfully plug a very difficult hole to fill. We’ve done it.”