SAN DIEGO -- The euphoria of the San Diego Chargers' stunning win against the defending Super Bowl champion Indianapolis Colts was replaced by reality Monday.

While two-time NFL rushing champion LaDainian Tomlinson said he should be able to play in Sunday's AFC championship game, the Chargers know quarterback Philip Rivers will be gimpy with a sprained right knee if he's able to play against the undefeated New England Patriots.

Rivers was listed as questionable. He injured his medial collateral ligament when he landed awkwardly after completing a 56-yard screen pass to Darren Sproles for a touchdown on the final play of the third quarter in Sunday's 28-24 upset of the Colts.

Coach Norv Turner compared Rivers' situation with that of tight end Antonio Gates. Gates dislocated his left big toe in a wild-card win over Tennessee, sat out practice all week and then played against the Colts.

"Right now, it's probably questionable in terms of playing in the game, but he's got a chance," Turner said Monday. "That will be a day-to-day thing and we'll monitor it as the week goes on."

Rivers was having tests on the knee and wasn't available to the media. He completed 14 of 19 passes for 264 yards and three touchdowns against the Colts before leaving. Rivers went to the locker room during the game and returned to the sideline with a brace on the knee, but didn't get back in.

Billy Volek took over and led the go-ahead drive, scoring the winning touchdown on a 1-yard sneak.

San Diego had to rely on other backups on Sunday, namely running backs Michael Turner and Darren Sproles.

The Chargers already are huge underdogs against the Patriots, and the injuries won't make it any easier.

"I'm concerned," Turner said. "I mean, I'm real concerned. We're lucky, or we're fortunate, to have a Darren Sproles, have a Michael Turner, have a Brandon McKinney, but you can only withstand so many hits.

"And obviously Billy played great and went in and did the things he had to. But we're getting ready to play the best team in the National Football League. We need to rally the troops and get everyone as healthy as we can be. I've been saying it since August, we want to be at our best. I hope we haven't played our best game yet. That's what we're trying to get done this week."

Rivers sprained his left knee against Tennessee on Dec. 9 and hobbled off the field. He returned and played well in the second half, throwing a touchdown pass to Gates with 9 seconds left to force overtime. The Chargers won it on Tomlinson's TD run.

The Chargers were without Tomlinson for a good deal of the Colts game after he hurt his left knee in the second quarter. He said he expects to play against the Patriots.

"It's nothing serious, just a hyperextension," Tomlinson said. "I think they've got me listed as questionable, but I'm pretty sure I'll be able to play. Obviously, I'm going to do all I can to practice. I don't want to miss any time to practice."

Tomlinson carried only seven times, for 28 yards, and caught one pass for 20 yards. He's rushed for just 70 yards in San Diego's two playoff wins.

Tomlinson and Rivers said on Sunday that they felt they could have gone back in if needed. But Turner said it was a medical decision to keep Tomlinson on the sideline.

"He couldn't have gone in, is the way I understand it," Turner said.

The coach added that the screen pass Sproles scored on had been designed for Tomlinson.

"But I felt great about the play with Darren in, and he obviously responded."

Turner said Gates' toe is "no worse than it was last week. I would think it would be late in the week or Sunday, go out and warm up again and see how he feels."

The Chargers say they're a much different team than the one that was blown out 38-14 by Tom Brady, Randy Moss and the rest of the Patriots in the season's second game. That was when the Chargers were stumbling to a 1-3 start. They righted their early season wrongs by winning 12 of 14, including eight straight.

"Obviously it was a long time ago from week two, but it's still going to be a heck of a challenge," Tomlinson said.

"You appreciate getting an opportunity to play them," he added. "We know how good they are. We played them obviously in week two, but we have played them in years past. And they've always been good. They've always kind of been that benchmark team that everybody looks to and so it's just a great opportunity to get a chance to play against possibly the greatest team to ever play."

The Chargers also lost to the Patriots in last year's divisional round, falling 24-21 after going an NFL-best 14-2 in the regular season.

Notes: Other injuries were DT Jamal Williams (ankle), DE Luis Castillo (ribs) and CB Antonio Cromartie (sore knee). Turner said they should be all right. Fullback Lorenzo Neal returned to practice last week for the first time since breaking his lower left leg at Tennessee on Dec. 9, but was inactive against the Colts. Turner thinks he'll be ready to play this Sunday.

Copyright 2008 by The Associated Press.