Source: Kevin Kolb set for tests

GLENDALE, Ariz. -- Arizona Cardinals quarterback Kevin Kolb injured his ribs while being sacked against the Buffalo Bills on Sunday.

Kolb will undergo additional tests Monday, a league source told ESPN NFL Insider Adam Schefter.

Kolb was injured with just more than two minutes left in the fourth quarter of Sunday's 19-16 overtime loss when he tried to fall forward and two Bills players landed on him. He lay on the field for several minutes as medical personnel attended to him, then gingerly walked off the field after a cart was waved off.

Kolb lost a tight battle to be Arizona's starter to open the season, but started four games after John Skelton sprained his right ankle in the opener against Seattle.

Skelton, who was active for the first time since his injury, replaced Kolb in Sunday's game. He went 2 for 10 for 45 yards and an interception.

Kolb finished 14 of 26 for 128 yards, with one touchdown and one interception.

Information from ESPN NFL Insider Adam Schefter and The Associated Press was used in this report.