Miami Dolphins' Ronnie Brown, center, is helped off the field with an ankle injury during third-quarter NFL football action against the Tampa Bay Buccaneers in Miami, Sunday, Nov. 15, 2009. (AP Photo...

WASHINGTON - OCTOBER 28: National Football League Commissioner Roger Goodell (L) testifies with others before the House Judiciary Committee about football brain injuries on Captiol Hill October 28, 2009 in Washington...

...in drills during an NFL football training session on Sunday, Aug. 16, 2009, in Englewood, Colo. Marshall has been sidelined the past two weeks to take care of a leg injury and be at his...

...Bengals training room, Monday, Sept. 10, 2007, in Cincinnati, urges NFL football players to keep their heads up when they tackle to help prevent injuries. (AP Photo/Al Behrman

...coach Perry Fewell talking with an assistant coach during an NFL game against the Jacksonville Jaguars, in Jacksonville, Fla. With a rising amount of injuries, Fewell doesn't have much time to regroup as the...

FILE - These are 2009 file photos showing Green Bay Packers football players Al Harris, left, and Aaron Kampman. Green Bay cornerback Al Harris and li...

...Redskins offensive tackle Chad Rinehart (75) is carted off the field following an unknown injury by emergency personnel during an NFL football game against the Dallas Cowboys, Sunday, Nov. 22, 2009 in Arlington, Texas. The...

...Betts (46) sits on the trainers table after having his left knee wrapped following an injury during an NFL football game against the Dallas Cowboys, Sunday, Nov. 22, 2009 in Arlington, Texas. The Cowboys...

...York Giants in the third quarter of an NFL football game, Sunday, Nov. 22, 2009, in East Rutherford, N.J. Turner is out with an injury. The Giants won 34-31. (AP Photo/Kathy...

...fourth quarter of an NFL football game against the St. Louis Rams Sunday, Nov. 22, 2009, in St. Louis. Warner left the game in the second quarter after an injury, but Arizona went on...

...third quarter of an NFL football game against the St. Louis Rams on Sunday, Nov. 22, 2009, in St. Louis. Warner was taken out of the game after an injury in the second quarter...

...medical personnel treat wide receiver Josh Cribbs after an injury on the final play of a 16-0 loss to the Baltimore Ravens in an NFL football game on Monday, Nov. 16, 2009, in Cleveland...

...is carried on a backboard after suffering an injury on the final play of the Browns' 16-0 loss to the Baltimore Ravens in an NFL football game Monday, Nov. 16, 2009, in Cleveland...

Miami Dolphins' Ronnie Brown, center, is helped off the field with an ankle injury during third-quarter NFL football action against the Tampa Bay Buccaneers in Miami, Sunday, Nov. 15, 2009. (AP Photo...

...before the Cardinals' NFL football game against the Chicago Bears in Chicago. Morey says he played with a concussion against the Bears despite his role raising awareness about the head injuries. (AP Photo/Nam...