Athletics designated hitter Brent Rooker will undergo surgery to repair a cartilage tear in his left knee and miss the remainder of the season.

“This is a big blow,” manager Mark Kotsay said Wednesday before the A’s played the Los Angeles Dodgers. “It’s a middle-of-the-order bat. It’s a guy that produced for us offensively for the last three seasons with 30-plus homers.

“There’s not one guy that is going to come in here and step in with that type of production. We’ll do our best to fill that void and make the best of the situation.”

The tear was discovered during an examination Tuesday at Stanford.

A two-time All-Star, Rooker hasn’t played since June 8.

Rooker played in all 162 games in 2025 but was in and out of the lineup this season due to his knee and a nagging oblique issue. The 31-year-old slugger was batting .200 with 10 home runs and 29 RBIs before he was placed on the injured list June 12, retroactive to June 9.

In addition to Rooker being sidelined, three other A’s starters landed on the IL in late June: infielders Zack Gelof (bruised right hand) and Jacob Wilson (right thumb inflammation), and left fielder Tyler Soderstrom (left hip impingement).

The A’s are moving to Las Vegas in 2028, beginning play in a ballpark being built on the Strip.

Athletics prospect Ryan Lasko was in stable condition after undergoing back surgery Tuesday night following a scary collision with minor league teammate Devin Taylor during a Double-A game in Frisco, Texas.

Dr. Jonathan Poggi performed the spinal decompression and stabilization operation at Texas Health Presbyterian Hospital Plano to address a fractured C6—C7 vertebra.

Lasko is an outfielder with Double-A Midland. He and Taylor dove into each other trying to catch a flyball, and Lasko remained motionless on the field after the play.

“I’ve been in touch with Ryan’s mom, Patti, to pass along the organization’s support and to let her know that all of us, throughout our system, have them in our thoughts and prayers,” A’s general manager David Forst said in a statement Wednesday. “We are incredibly grateful to Noah Huff and Audy Merrick, our athletic trainers in Midland, for their on-field actions last night, as well as to the Frisco RoughRiders and the paramedics on the scene.

“We are encouraged by the reports and updates from Dr. Poggi, and we will continue to put all of the resources of our medical staff towards supporting Ryan and his recovery.”

Forst added that player development director Ed Sprague was traveling to Frisco and counseling will be available to players.

The 24-year-old Lasko was selected by the Athletics in the second round of the 2023 amateur draft from Rutgers. He was batting .209 with six homers, 34 RBIs and a .635 OPS for Midland this season.

Lasko appeared in 13 games at Triple-A Las Vegas last year. He also played 21 games in the Arizona Fall League for promising prospects, batting .357 with nine stolen bases.