RB Ryan Mathews not practicing

SAN DIEGO -- Injured in the first half of last week's loss to the Oakland Raiders, San Diego Chargers running back Ryan Mathews was not on the field during the early portion of his team's practice Thursday.

Mathews appeared to suffer a concusion on a 5-yard run in the second quarter, taking a knee to the head from an Oakland defensive player. San Diego coach Mike McCoy said that in order for Mathews to return to the field, he will be subject to passing the NFL's protocol for concussion testing.

Other players not on the field for the early portion of Thursday's practice include outside linebacker Jarret Johnson (leg), cornerback Johnny Patrick (chest) and offensive linemen Chad Rinehart (toe) and D.J. Fluker.

Fluker did not appear to suffer an injury during the Oakland game but had his right knee wrapped as he watched practice from the sidelines. Nick Becton played right tackle with Fluker out.

The Chargers did receive good news, with left tackle King Dunlap getting the clearance from trainers to practice, after he missed two games with lingering concussion systems. Dunlap worked at left tackle with the first unit.

New offensive lineman Mike Remmers is wearing No. 60. New defensive lineman Lawrence Guy is wearing No. 71. New practice squad additions include tight end Ryan Otten (No. 82) and running back Kerwynn Williams (No. 30).

With Johnson out, the Chargers are thin at outside linebacker. Larry English, Tourek Williams and Thomas Keiser are the only guys available on the active roster