PORT CHARLOTTE, Fla. - The Tampa Bay Rays, who led the American League with 60 saves last year, will have to cover a major gap in their bullpen for at least the first month of the season.

All-Star closer Brad Boxberger, whose career-high 41 saves were tops in the AL in 2015, will miss eight weeks after undergoing surgery to repair a core-muscle injury, manager Kevin Cash said.

The loss significantly weakens a Rays team that is hoping to improve on last’s year’s 80-82 record by relying on a sturdy pitching staff.

“Obviously it’s a blow, because he’s so valuable to our team, to our staff and especially at the back of the game,’’ Cash said, “but we have a number of guys who can try to fill that void for the first month of the year.’’

They include Alex Colome, Steve Geltz, lefty Xavier Cedeno and newcomers Ryan Webb and Danny Farquhar, who saved 16 games for the Seattle Mariners in 2013. None of them will be designated the closer, said Cash, who will instead decide on his ninth-inning reliever based on matchups.

Boxberger, 27, had been a setup man during his previous three seasons before emerging as the bullpen’s anchor last year, when he went 41-for-47 in save chances while relying on a fastball-changeup combination.

He became more hittable in the second half, when his ERA zoomed to 4.33 for an overall mark of 3.71. Boxberger also lost 10 games, an inordinately high number for a closer.

Cash said Boxberger did not get hurt in any specific play, but was instead dealing with nagging pain from the injury that eventually became too troublesome to keep pitching.

With a solid rotation headed by Chris Archer, the Rays are looking to bounce back from consecutive losing seasons after making the playoffs four times from 2008-2013. Their bullpen depth will be tested in Boxberger’s absence.

Said Cash: “We have multiple options that we’re excited to see how it shakes out.’’