Quarterbacks Robert Griffin III and Matt Cassel were knocked out of their games with head injuries Sunday, and Steelers star safety Troy Polamalu limped off the field after aggravating his strained right calf.
Redskins rookie Griffin sustained a ``mild concussion,'' according to coach Mike Shanahan, when he took a shot to the helmet while scrambling to try to avoid a sack during Washington's 24-17 loss to the Atlanta Falcons. Griffin left the game about 10 minutes in to the second half and did not return. He also was treated for a cut on his chin.
``He wasn't sure what quarter it was in the third quarter. So at that time, when he wasn't really sure what the score was, what the quarter was, we knew he had a mild concussion - at least according to the doctors,'' Shanahan said.
Team spokesman Tony Wyllie said Griffin was examined by a neurologist in the locker room before being sent home from the team's stadium and will be evaluated again Monday. NFL rules require a player diagnosed by the team medical staff with a concussion to sit out the rest of the game. The player also can't return to practice or game action until a team doctor and independent neurologist clear him.
About three hours after the game, Griffin wrote on Twitter: ``I'm ok and I think after all the testing I will play next week.''
Cassel, Kansas City's quarterback, left with a head injury in the fourth quarter after getting hit by Baltimore's Haloti Ngata while attempting a pass. Cassel remained flat on his back for several minutes before getting helped up and walking off the field under his own power. Backup Brady Quinn entered the game to a round of applause.
Cassel was 9 of 15 for 92 yards and two interceptions when he left the game won by Baltimore 9-6.
Polamalu left Pittsburgh's 16-14 win over the Philadelphia Eagles in the first quarter. He limped off following a fumble by Eagles quarterback Michael Vick. The 2010 NFL Defensive Player of the Year watched the entire second quarter from a seat on the bench and did not move. He was replaced by backup Ryan Mundy.
Polamalu missed each of Pittsburgh's previous two games after injuring the calf in a season-opening loss in Denver.
The Steelers also lost linebacker LaMarr Woodley with a strained right hamstring.
Browns middle linebacker D'Qwell Jackson left Cleveland's 41-27 loss to the Giants with a concussion and did not return.
Jackson, one of the team's defensive leaders, was hurt in the second quarter, when the Browns allowed 20 points. The Browns also lost starting cornerback Dimitri Patterson in the second half to an ankle injury.
The Giants also lost a player to a head injury when backup running back Andre Brown took a hard hit on a kickoff runback.
Titans running back Javon Ringer was carted off the field in the fourth quarter of a 30-7 loss to the Minnesota Vikings with a left knee injury.
Ringer was injured with just over three minutes to play after catching a pass near the sideline and heading up the field. Vikings cornerback Josh Robinson wrestled him to the turf, twisting the running back down awkwardly.
Ringer's knee appeared to buckle as he went down, and he immediately grabbed it in pain as teammates gathered around him. There was no immediate word on the severity of his injury.
New Orleans starting cornerback Jabari Greer left Sunday night's 31-24 win over San Diego because of what team officials called a hip injury.
Greer was hurt late in the second quarter and did not return, a blow for a New Orleans team already ranked last in the NFL in defense.
Second-year pro Johnny Patrick took over for Greer, with rookie Corey White entering on passing downs as the nickel back.