"It's a very, very difficult situation," Seahawks coach Pete Carroll said of Farwell. "He had extensive damage [Friday night in the game against the Chicago Bears]. Heath is going back East to get evaluated and probably will need surgery."
For Farwell, 32, this could mean the end of his NFL career. Farwell was in a tough battle for a roster spot at linebacker, especially with the emergence of rookie Brock Coyle as a Mike linebacker and special teams contributor.
The good news at middle linebacker was the return of starter Bobby Wagner, who has missed most of the preseason with a hamstring injury.
"It has been a long haul for him waiting it out," Carroll said of Wagner. "But he's ready to go and looked very good [Monday]."
Wagner did not play in the first three preseason games, so he said he would like to get on the field some in the final preseason game Thursday night at Oakland.
"I feel great," Wagner said Monday. "I really got tired of watching everybody else. I'd like to get out there to get a feel for the game, but I've been doing this a long time, so I think I'll be fine."
Cornerback Jeremy Lane, who had his best preseason game Friday with five tackles and an interception, did not practice Monday because of a sore groin.
"We don't know how serious it is," Carroll said of Lane's injury. "We checked it out and it looks like it's going to be OK. But he has to respond and come back, so we don't know. We'll check him again [Tuesday]."
Tight end Cooper Helfet did not practice Monday after suffering a bruised knee in Friday's game.