SAN DIEGO -- Philip Rivers took half the practice repetitions on Thursday and said his sprained left knee is improving.

However, he stopped short of saying he'll be the Chargers' starting quarterback on Sunday against Detroit.

"That's the plan, but it's not Sunday," Rivers said. "You don't have to know right now."

Rivers split the repetitions with backup Billy Volek, who is being prepared in case Rivers can't play or suffers a setback during Sunday's contest.

Rivers wore a brace on the knee as he practiced. He said he has made progress in terms of recovering from the injury he suffered against Tennessee last Sunday.

Yet he also remained cautious while meeting with reporters.

"I felt good," Rivers said. "It's getting better. How you feel on Thursday isn't always how you're going to feel on Sunday. But it has certainly got a lot better."

Coach Norv Turner said Rivers wasn't held to a lower practice standard because of his injury and said Rivers looked good.

"I thought he threw the ball well," Turner said. "I thought he moved well in what we asked him to do. We'll just do a little bit more with him (today)."

The Chargers (8-5) take a three-game winning streak into the game against the Lions (6-7) and can clinch the AFC West crown with a victory. Rivers fueled last Sunday's comeback from a 14-point deficit by playing well in the fourth quarter and overtime of a 23-17 victory.

Rivers injured the knee in the second quarter after being clipped by Tennessee's Antwan Odom. He missed the rest of the first half before returning.

Despite hobbling around practice Thursday, Rivers said he's not worried about injuring the knee further if he plays.

"As in any game, you're somewhat at a risk just by walking on the field, at 100 percent or if not," Rivers said. "Yeah, the fact that it doesn't increase the chance of being further injured, certainly that makes you feel better."

While Rivers practiced Thursday, two other key players didn't. Tight end Antonio Gates (back, hip) and defensive tackle Jamal Williams (ankle) both missed practice.

Gates said he's still feeling pretty sore.

"I'm making a real push at this thing," Gates said. "I'm trying hard. I'm doing a lot of different things. I ran a little bit and I felt good. But it is still sharp pain because it is deep and it was a hard fall."

Starting right guard Mike Goff was a limited practice participant and plans to play Sunday. Goff has made 61 consecutive starts since joining the Chargers in 2004 and said he expects to play every snap against the Lions.

"If it comes to the point where I would be hurting the team, then that's when I would put the streak behind because this is more important than any one person," Goff said. "It's something I take self-pride in. I've been able to play through some things and I look forward to continuing that but if there ever comes a time where I don't think I can go, I just need to accept that. If somebody can do it better than I can, then it's time for me to step aside."

Rookie receiver Craig Davis was a limited practice participant after injuring an ankle while running a route during Thursday's practice. Turner said Davis was experiencing soreness in the Achilles' tendon.

Contact staff writer Mike Sullivan at (760) 739-6645 or msullivan@nctimes.com.