updated 4:33 p.m. PHOENIX (AP) - Kevin Kolb's star-crossed career in Arizona has taken another hit. The Cardinals announced Tuesday that Kolb has rib cartilage damage and will be sidelined for "an unspecified period of time." The job will revert to Skelton, who beat out Kolb in the preseason and just now is returning to health from a sprained left ankle. Skelton was active on Sunday for the first time since the injury. Kolb also has a sprained sternoclavicular joint. Known commonly as the SC joint, it connects the breastbone to the collar bone. The damage was discovered in an MRI on Monday. The exam did not show any fractures on the ribs or sternum, which would have been far more serious. The injury comes with Arizona entering arguably the toughest stretch of its schedule. Kolb will miss Sunday's game at Minnesota and most likely the Oct. 29 Monday night showdown at home against San Francisco. The team is at Green Bay on Nov. 4, then has a bye week before traveling to Atlanta. He changed the call to a draw play at the line of scrimmage but running back William Powell didn't realize it. That left the ball in Kolb's hands. He tried to scramble but was tackled a yard shy of the line of scrimmage, the ball pinned between his ribs and the turf. The play was not one of the five sacks Kolb sustained, one for a safety. Kolb has been sacked 22 times in the past three games - the last two losses after the team opened the season 4-0, the franchise's best start in 38 years. In six games, Kolb has completed 60 percent of his passes for 1,169 yards with eight touchdowns and three interceptions. It's the third time Kolb has been sidelined with an injury in 22 games since he arrived in Arizona. Last season, in the Cardinals' sixth straight loss, he went out with a turf toe injury. With Skelton at the controls, Arizona won three of the next four. Kolb returned to lead the Cardinals to an overtime victory over Dallas. But the following week against San Francisco, he took a knee to the head on Arizona's first series and left with a concussion. Kolb didn't play the rest of the season as the erratic but resilient Skelton led the Cardinals to an 8-8 finish. Coach Ken Whisenhunt declared an open competition between Skelton and Kolb and announced Skelton the winner just before the final week of practice leading to the season opener. Skelton, though, had to be carted off the field with the sprained ankle in the fourth quarter against Seattle. Kolb, who entered the game to boos from the home crowd, directed the winning touchdown drive in a 20-16 victory. A stunning win at New England, followed by victories over Philadelphia and Miami made Arizona one of just three NFL teams to start 4-0, but the Cardinals were dominated in a 17-3 Thursday night loss at St. Louis, with Kolb taking brutal hit after brutal hit, including nine sacks. Last Sunday, in a typically wild Arizona home game, the Cardinals' Jay Feely kicked a franchise record 61-yard field goal to tie it, only to have his 38-yard attempt to win the game deflected. The ball hit the left upright and bounced out. In overtime, Skelton threw an interception that set up Buffalo's game-winning kick. Kolb completed 14 of 26 passes for 128 yards against the Bills. He threw for a touchdown and was intercepted once. The scrambler also rushed for 66 yards in 5 carries, 22 on the play before he was hurt. Skelton, a 6-foot-6, strong-armed pocket passer, is 8-4 as a starter after being drafted in the fifth round out of Fordham. In his career, he has completed 52 percent of his passes for 2,769 yards and 13 touchdowns with 18 interceptions. In his brief time this year, Skelton is 16 of 38 for 194 yards and no TDs with two interceptions. Like Kolb, Skelton is a Texan - Kolb from Stephenville and Skelton from El Paso. With Skelton finally healthy, Whisenhunt would have been on the spot to officially name Kolb the team's starter or return the reins to Skelton. Kolb's injury made the decision for him. Rookie Ryan Lindley, a sixth-round draft pick from San Diego State, is Skelton's backup. Follow Bob Baum at www.twitter.com/Thebaumerphx