Head injuries were an important issue for the NFL in the offseason, and several key players went down with concussions on the first full day of play.

Philadelphia's Kevin Kolb and Carolina's Matt Moore were sidelined Sunday by concussions — and quarterbacks weren't the only ones left groggy by big hits. New York Giants tight end Kevin Boss and Eagles linebacker Stewart Bradley sustained similar injuries in their season openers.

Detroit Lions quarterback Matthew Stafford was knocked out against Chicago with a right shoulder injury following a blindside sack by Julius Peppers.

The league recently implemented new return-to-play guidelines for players who sustain concussions in practice or a game, and each team must consult with an independent neurologist whenever there is a head injury.

Kolb was forced out against Green Bay, ending his first start in the post-Donovan McNabb era after one half. He was hurt in the second quarter when he was tackled from behind by Packers linebacker Clay Matthews. The quarterback fumbled the ball out of bounds and was slow to get up.

Making his third career start, Kolb was looked at by trainers for several minutes on the Eagles' sideline. He returned to the game for one more series and threw three short incomplete passes.

Kolb went 5 of 10 for 24 yards and was sacked twice. He was one of several Eagles injured in the game. Bradley also sustained a concussion — and returned to play after his collision. Pro Bowl fullback Leonard Weaver (knee) and center Jamaal Jackson (elbow) did not return from their injuries. Left tackle Jason Peters sprained his right knee, yet stayed in the game.

Weaver has a torn ACL in his right knee and Jackson has a torn biceps in his right arm.

Stafford's status for Detroit's next game is uncertain. He said he will go through tests this week and is not sure if he'll be ready to play against Philadelphia.

"I don't know, we'll see," Stafford said. "I will try, though."

Bears running back Matt Forte had just scored an 89-yard touchdown on a screen pass to pull Chicago to 14-10 when Stafford went down. He was hit in the shoulder by Peppers as he dropped back to pass and landed on it, the ball coming loose in the process.

Moore was injured late in the fourth quarter after being sacked by Giants defensive end Osi Umenyiora near his own goal line. Moore, who fumbled on the play, walked gingerly off the field with athletic trainers by his side. Panthers coach John Fox said after the game that Moore sustained a concussion.

Boss was knocked out of the game with a neck injury and concussion in the first quarter, and Giants special teams captain Chase Blackburn injured a knee late in the second quarter.

Boss was hurt after being hit in the back of the neck by Panthers safety Sherrod Martin on New York's fourth play from scrimmage. Boss was on the ground when he was hit on the incomplete pass. He was taken off the field on a cart.

Carolina wide receiver Charly Martin also sustained a concussion.

Buffalo's already banged-up linebacking group could be down another key player after Paul Posluszny sustained what was described as a potential long-term knee injury.

Bills coach Chan Gailey said it's too early to determine the severity of the injury because Posluszny is scheduled to have further tests following a 15-10 loss to Miami. Though Gailey said the injury could be "short term," he didn't rule out the possibility that it could be significant.

Posluszny was hurt on the first play of the third quarter when he was one of three Bills defenders to bring down running back Ronnie Brown along the sideline. Posluszny sat on the field for several minutes before getting up on his own.

Houston Texans defensive end Connor Barwin was carted off the field against Indianapolis with a right leg injury. Barwin went down in the first quarter when Houston defensive tackle Antonio Smith accidentally slid into him while they were chasing Joseph Addai on a running play. Barwin ripped off his helmet in obvious pain, and Houston coach Gary Kubiak joined medical staff on the field.