COSTA MESA, Calif. -- A surprise addition to the injury report on Thursday, Los Angeles Chargers receiver Keenan Allen did not practice on Friday due to a shoulder injury and has been listed as questionable for Sunday’s game against the Denver Broncos.

Allen is the Chargers’ leading receiver with 33 receptions for 446 receiving yards and a touchdown on 56 targets. The Cal product also leads the NFL in third-down receptions with 18 for 279 receiving yards, so it would be a big blow to the Chargers’ offense if Allen can’t play this weekend.

However, Chargers coach Anthony Lynn said he’s hopeful that Allen can play on Sunday. Allen suffered the injury on a fall to the ground during Thursday’s practice.

“He wants to play, but we’ve got to do what’s best for Keenan,” said Lynn, who chose to rest Allen on Friday to provide an extra day of recovery. “He fell down yesterday in practice, and that’s sore. It’s day to day right now.”

In his fifth season with the Chargers, Allen has struggled to stay on the field. Allen has finished the year on the injured reserve the last three seasons, and has missed a total of 25 games due to injury since the Chargers selected him in the third round of the 2013 draft.

Along with Allen, right tackle Joe Barksdale (foot) and defensive tackle Corey Liuget (back) did not practice on Friday and are listed as questionable for Sunday.

Lynn said Barksdale will be a game-time decision. Running back Melvin Gordon (shoulder) was a limited participant on Friday and is listed as questionable. However, Gordon is expected to play against the Broncos.

Safety Adrian Phillips was full participant on Friday but was listed as questionable because he has yet to pass the NFL’s concussion protocol.