Gradkowski injured his left knee while getting sacked in the first quarter and then the right while trying to avoid a pass rusher in the closing minute of the first half. Gradkowski was diagnosed with a torn medial collateral ligament in his left knee and a partially torn MCL in his right knee.
He will have an MRI on Monday and says he will do whatever he can to get back on the field during the final three games, even if that appears unlikely at this point. Coach Tom Cable said he would address the quarterback position for next week's game on Monday.
Gradkowski had provided a spark since replacing Russell as starting quarterback for Oakland last month. He won two of his three starts, engineering comeback victories against Cincinnati and Pittsburgh before the injury. The Raiders trailed 17-10 when he got hurt before losing 34-13.
"It's just tough," he said. "It's tough because the past couple weeks I felt gave us great positive attitudes and energy, and then this happens. But you know stuff happens for a reason. We just have to battle back and we'll be all right."
Gradkowski completed 10 of 18 pass attempts for 153 yards in the first half against the Redskins, leading the Raiders to 10 points. Russell struggled when he came in, going 10 for 16 for 74 yards and an interception, while getting sacked six times. The Raiders gained just 39 yards in the second half.
Oakland allowed eight sacks in all, their most since allowing nine in a loss at Seattle in 2006. Russell was visibly upset, yelling at his offensive linemen at times in the second half.
"He was definitely frustrated," tight end Zach Miller said. "We didn't protect Bruce well today, and we didn't protect JaMarcus either. You can't do that. You have to give your quarterback time to throw."
Russell, the No. 1 overall pick in the 2007 draft, lost his starting job last month after completing just 46.8 percent of his passes and committing 14 turnovers in his first nine starts.
Cable would not say whether Russell or third-stringer Charlie Frye would start if Gradkowski is unavailable against Denver next Sunday. Cable said he still believes Russell can be an effective NFL quarterback despite his early struggles.
"I think the guy can succeed," Cable said. "I've not ever said he couldn't or didn't think he couldn't or anything like that. So for me, it's just getting him where he needs to be to succeed."
Russell did not address the media after the game.