The Chargers didn't say to what degree the ligament was injured, which would help narrow down how long Mathews is expected to be out.
"In all fairness to him and the training staff, everyone recovers differently," coach Mike McCoy said Monday. "I'm not a doctor by any means so I can't look at an X-ray or a picture and say, 'Oh it's going to be this long.' We've had players who were supposed to be done for the season and the next thing you know they come out there Monday or Wednesday and they're practicing with something torn or something broken or this or that. I don't want to put a timetable on anything. It's unfortunate but it's part of the game."
Mathews, who is in the fifth and final year of his contract, was injury-prone in his first three seasons. Last year was the first time he played all 16 regular-season games, rushing for a career-high 1,255 yards. He did sprain an ankle late in the season but played through it until finally being forced to the sideline during the Chargers' divisional-round playoff loss at Denver. Mathews also has had trouble holding onto the ball during his pro career.
The Chargers (1-1) have Danny Woodhead, Donald Brown and rookie Branden Oliver at running back.
This was the kind of situation the Chargers envisioned when they signed Brown in the offseason as an unrestricted free agent from the Colts, who drafted him in the first round in 2009.
McCoy said he expects Brown to step in just as Rich Ohrnberger stepped in at center after Nick Hardwick was lost for the season following the opener due to a recurring neck stinger.
"Donald's played a ton of football," McCoy said. "The number of snaps he got in Indy in a very similar system, when he was with Peyton (Manning), so coming here we knew exactly what he can do. We've got a lot of confidence in him. We've said that we're going to play all our backs, certain rotations, certain number of plays. Some weeks it's going to be more than others and it's the second week in and they'll take a few more snaps. We have confidence in all our players. That's why they're here."
The Chargers say nothing changes in the wake of their big victory over the defending Super Bowl champions. Tight end Antonio Gates caught three touchdown passes from Philip Rivers and the offense controlled the tempo to help keep Russell Wilson and Marshawn Lynch off the field.
Up next is a trip to Buffalo, which leads the AFC East.
"Victory loves preparation," Ohrnberger said. "It's a motto we have in the offensive line room. It's something that's important to us. Regardless of the opponent, we're going to respect them just the same. The defending world champs came in here yesterday, and we're going to prepare for the Buffalo Bills, who are 2-0, just the same way we did for Seattle. That's just it. It's all in the preparation. You've got to give all these teams respect."
