DAVIE, Fla. -- Dolphins quarterback Jay Fiedler will start next Monday night against the Chicago Bears after sitting out six weeks with a broken right thumb.

Ray Lucas, who started at quarterback Sunday, underwent an MRI exam Monday, but results will not be available until Wednesday.

Lucas was knocked out of the game in the third quarter with a deadened nerve in his shoulder and neck.

Fiedler played in the third and fourth quarters in a 38-21 loss to the Buffalo Bills in the snow Sunday. He reported no lingering problems with the thumb despite throwing an interception on a wobbly pass.

"He told our doctors he felt great as far as his hand,'' Dolphins coach Dave Wannstedt said. "He was really happy he was able to get some snaps and run around a little bit. You could see from quarterbacks that have been hurt and come back and play, it takes some time to get into the game-speed rhythm again.''

The loss ended the Dolphins' two-game winning streak and dropped their record to 7-5. Miami is in a tie for first place in the AFC East with New England, while Buffalo is a game behind at 6-6.

Lucas was 6-for-11 for 40 yards and one touchdown against the Bills, and Fiedler went 5-for-9 for 15 yards and one interception. The Dolphins are 2-4 in games Lucas has started after beginning the season 5-1 under Fiedler, who broke his right thumb against Denver on Oct. 13.

Fiedler's return would allow the offense to regain some balance. Running back Ricky Williams ran for 228 yards against the Bills.

"We're one of the top five teams rushing the football. We just need to maintain that,'' Wannstedt said. "Once we get Jay back, we'll be able to get into hopefully a little more of a routine, and our passing game will improve.''

Fiedler is 117-of-185 for 1,304 yards, nine touchdowns and seven interceptions this season.

Lucas was sacked from the blind side early in the third quarter by blitzing Bills linebacker Keith Newman, who broke through the line unblocked and slammed into Lucas' back.

Lucas lay on the icy field for several minutes before slowly walking off. He was aided by four trainers as tears welled in his eyes. Lucas was taken to the locker room for precautionary X-rays and did not return.

The Dolphins released third-string quarterback Dave Dickenson on Tuesday. Dickenson signed with Miami on Oct. 15 and served as the third quarterback for five games behind Lucas and Sage Rosenfels. He was inactive last week against the Bills and did not appear in any games for the Dolphins.

The former Canadian Football League MVP was released by San Diego and Seattle earlier this year.