NFL: Kevin Kolb hurts knee after slipping on mat

Quarterback Kevin Kolb's chances of earning the Buffalo Bills' starting job were nearly upended by a wet and slippery rubber mat.

Kolb, the former Eagles quarterback who is locked in a competition with rookie first-round pick EJ Manuel, avoided serious injury to his left knee when he slipped and stumbled awkwardly while switching fields between practice drills Saturday.

Coach Doug Marrone said the injury does not appear to be serious. He called it "a bump," and listed Kolb as "day by day."

Marrone also provided an update on the status of Stevie Johnson, saying the team's No. 1 receiver will miss at least a week with a pulled left hamstring. Johnson was hurt in practice Friday.

Kolb wasn't available for comment, but showed frustration by angrily tossing his helmet to the ground before being examined by head trainer Bud Carpenter. After a few minutes, Kolb got up on his own and was escorted to the locker room.

Kolb was joining the quarterbacks and receivers in making their way through a tunnel to work out on an adjoining field.

Patrick Peterson is catching passes, throwing some, and running with the ball during training camp.

No doubt about it, new Arizona Cardinals coach Bruce Arians has plans for the dynamic player on offense.

In his first two NFL seasons, Peterson made the Pro Bowl as a punt returner, then as a cornerback. He remains a shutdown cornerback, first and foremost. And he still plans to return punts.

But Arians said Peterson is too talented to be standing on the sideline all the time when the Cardinals have the ball.

Peterson is all for it.

"I'm pretty dynamic with the ball in my hands," he said. "I'm not saying the offense needs help. They have great talent over there. But I guess [Arians] just wanted more explosive plays from guys that could help."

The Miami Dolphins could be the only legitimate challenger to New England's AFC East dominance.

The Dallas Cowboys hope they will be a true threat in the NFC East, where both the defending division champion Redskins and the Giants are more highly regarded.

For two teams with so many question marks heading toward the 2013 season, an extra exhibition game can't be a terrible thing - provided no key players get hurt in Sunday night's Hall of Fame game in Canton, Ohio.

Miami already has some injury concerns, with starting receivers Mike Wallace (groin) and Brian Hartline (left calf) hobbled in practice this past week.

Dallas quarterback Tony Romo had offseason surgery for a cyst on his back, and coach Jason Garrett has been close-mouthed on Romo's availability for the lone game this weekend. Only Dallas and Miami will play five exhibitions this summer.

The NFL will begin its new clear-bag policy for fans this weekend at the Hall of Fame inductions and game.

For security reasons, fans can no longer bring backpacks or large bags into stadiums. The NFL is ratcheting up its safety measures in the wake of the Boston Marathon bombing.

The only bags that can be taken into game venues are clear plastic, vinyl, or PVC that don't exceed 12 inches by 6 inches by 12 inches, including one-gallon clear plastic freezer bags.