Chargers wide receiver Joshua Palmer sidelined by a concussion

COSTA MESA — Already without their two top wide receivers, the Chargers might be missing a third one when they face the Denver Broncos on Sunday in Colorado. Joshua Palmer suffered a concussion during their loss to the Buffalo Bills last Saturday and didn’t participate in practice Wednesday.

Keenan Allen also didn’t practice because of a nagging heel injury that has sidelined him for the past two games. He worked out on the sideline while his teammates performed individual drills, running a series of sprints before heading to the locker room before team activities began.

Mike Williams has been sidelined since he sustained a season-ending knee injury during the Chargers’ victory over the Minnesota Vikings on Sept. 24. His absence has impacted the Chargers’ passing game with opponents focusing on Allen or on Palmer after Allen was injured.

It wasn’t immediately clear when Palmer was hurt. Chargers interim coach Giff Smith said Palmer reported to the team’s headquarters Sunday complaining of concussion symptoms and was promptly placed in the NFL’s protocol. It wasn’t certain whether he could play Sunday.

“It’s just day by day,” Smith said.

The Chargers hope Allen will be sound enough to play against the Broncos, but he hasn’t played since their loss to Denver on Dec. 10 at SoFi Stadium. Allen set a Chargers record with 108 catches in a season, breaking running back Austin Ekeler’s team record of 107 with six receptions in a 24-7 loss.

“We’ll see how it goes,” Smith said.

If the Chargers are without Palmer and Allen on Sunday, then the top available targets for quarterback Easton Stick would be tight end Gerald Everett with 46 catches, Ekeler with 43 receptions, rookie wide receiver Quentin Johnston with 33 catches and tight end Donald Parham Jr. with 22.

WHAT ABOUT DERWIN?

Chargers safety Derwin James Jr. played only 41 of 55 defensive snaps during Saturday’s game against the Bills, believed to be the fewest he’s played in a game in which he was not injured or ejected in a career that includes three Pro Bowl selections in his five healthy NFL seasons.

Most noteworthy was his absence during a key third-and-8 play in the fourth quarter in which Bills quarterback Josh Allen completed a pass to Stefon Diggs for an 11-yard gain and a first down right in front of the Chargers’ bench. Essang Bassey had replaced James and was beaten on the coverage.

Buffalo’s drive continued and Tyler Bass then kicked the winning 29-yard field goal with less than a minute to play in the Bills’ 24-22 victory. The loss dropped the Chargers to 5-10 and officially eliminated them from the AFC playoff race with two games remaining in the regular season.

“We were substituting, me and Bassey,” James explained Wednesday. “He was in and I was supposed to come back in, but I didn’t get a chance to go back out there. On that drive, I wasn’t in to start the drive, like two or three plays. It wasn’t just the third-and-8, I wasn’t in to start the drive.”

The game plan called for James to play what’s known as the “star” position in the Chargers’ defensive alignment, serving more like an additional linebacker or a defensive back stationed closer to the line of scrimmage. James normally drops into pass coverage as a strong safety.

James said it was uncertain if he would continue in that role Sunday.

“Probably not,” he said. “I’m not sure, but probably not.”

INJURY UPDATES

Outside linebacker Joey Bosa, who has been sidelined by a broken right foot since the Chargers’ loss to the Green Bay Packers on Nov. 19, was listed as a limited participant in practice Wednesday. The Chargers opened the 21-day practice window for him to return from injured reserve last week. … Outside linebacker Khalil Mack didn’t practice, taking advantage of his customary extra day of rest on Wednesdays. … Linebacker Kenneth Murray Jr. was listed as limited because of a shoulder injury.