Charles Tillman said that he experienced "extreme dizziness'' when he was hit in the back of the helmet in Sunday's loss at Minnesota.

That is what led the Bears to say he suffered a mild concussion. Tillman returned to the practice field this afternoon at Halas Hall and had full participation, making him likely to start Sunday's game vs. St. Louis unless there is an unforeseen setback.

"Really, it was just a hard hit to the back of my head, a big bump,'' he said. "I saw like a bright flash, dizziness more than anything. I was completely conscious. I knew what was going on the whole time. Just more less just dizziness. I was completely aware of my surroundings. I knew I was in Minnesota. I knew I was in the Metrodome. I knew I was in a football game."

The NFL released new guidelines for players returning to action from concussions on Wednesday, and Tillman passed all the levels of tests. Concussions have been at the forefront for the league, which had to appear on Capitol Hill before the House Judiciary Committee in late October. Quarterbacks Kurt Warner and Ben Roethlisberger sat out with concussions last week. Running backs Clinton Portis and Brian Westbrook have been sidelined. Running back Jamal Lewis was placed on inured reserve on Wednesday with post-concussion symptoms.

The Bears will have to follow a stricter NFL policy regarding concussions before cornerback Charles Tillman can return to the practice field or consider playing in Sunday's game against the St. Louis Rams.

Tillman was knocked out of Sunday's loss at Minnesota with what coach Lovie Smith has repeatedly called a "mild concussion.'' He did not practice today, and was seen driving out of the facility in the late morning.

Commissioner Roger Goodell notified teams today of an expanded return-to-play mandate for players who suffer concussions that takes effect immediately. The stricter guidelines was created by the league's medical committee on concussions in conjunction with the NFL Players Association.

The new statement reads:

"Once removed for the duration of a practice or game, the player should not be considered for return-to-football activities until he is fully asymptomatic, both at rest and after exertion, has a normal neurological examination, normal neuropsychological testing, and has been cleared to return by both his team physician(s) and the independent neurological consultant. A critical element of managing concussions is candid reporting by players of their symptoms following an injury. Accordingly, players are to be encouraged to be candid with team medical staffs and fully disclose any signs or symptoms that may be associated with a concussion."