Source: Saints' Derek Carr out indefinitely due to oblique

NEW ORLEANS -- Saints quarterback Derek Carr suffered an oblique injury in Monday night's loss to the Kansas City Chiefs, a source confirmed to ESPN. 

An MRI taken Tuesday confirmed the injury was to Carr's oblique, according to the source. The quarterback had said he thought he suffered the injury while throwing an incomplete pass toward the end of the 26-13 loss but needed to have additional testing to confirm. 

The source wouldn't put a timeline on how long Carr will be sidelined. 

Oblique injuries typically lead to multiweek absences. The Saints play two games in the 10 days -- Sunday against the Tampa Bay Buccaneers and then Oct. 17 against the Denver Broncos on "Thursday Night Football." 

If Carr cannot play, then either rookie Spencer Rattler or Jake Haener would take his place. Haener replaced Carr against the Chiefs.

The oblique muscles, or the abdominal muscles, can impact a quarterback because much of his throwing power comes from his core muscle instead of his arm. Carr said that he didn't leave the Chiefs game because of pain but because he would not be effective if he returned. 

"It wasn't like dealing with pain. ... I just can't do what I want to do," he said at the time.

Former Saints quarterback Drew Brees returned from a left oblique strain after sitting out two weeks of training camp prior to the 2014 season. Brees, who was 35 at the time of the injury, later admitted his mechanics suffered and he developed bad habits that season after rushing to get back in the lineup before he was fully healthy.

Carr has had four significant injuries while in New Orleans, although he did not miss time last year. He sprained the AC joint in his shoulder against the Green Bay Packers in Week 3 of last season and was placed in concussion protocol twice last year, exiting in losses to the Minnesota Vikings and Detroit Lions.

Carr was listed as having a left groin injury in Week 4 this season.

NFL Network first reported news that that additional testing confirmed that Carr's injury was to his oblique.