Arizona Cardinals quarterback Kevin Kolb suffered an injury in his rib/chest area while taking a sack in the fourth quarter of Sunday's 19-16 overtime loss to the Buffalo Bills.
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Kolb was injured with just over two minutes left in regulation when he tried to fall forward and two Bills players landed on him. He remained on the field for several minutes as medical personnel attended to him, then gingerly walked off the field after a cart was waved away.
Kolb lost a tight battle for the right to be Arizona's starter to begin the season, but he started four games after John Skelton sprained his right ankle in the opener against the Seattle Seahawks.
Skelton, who was active for the first time since his injury, replaced Kolb on Sunday and nearly led the Cardinals to a win.
Kolb suffered a similar injury in this season's Hall of Fame Game, exiting the 17-10 loss to the New Orleans Saints with a rib contusion.
The Associated Press contributed to this report.