Saints' Derek Carr in protocol, also being checked for rib injury

Derek Carr leaves the game after taking a huge hit (0:29)

Derek Carr appears injured on the ground after taking a huge hit from Bruce Irvin. (0:29)

METAIRIE, La. -- New Orleans Saints quarterback Derek Carr is in the concussion protocol after sustaining his second concussion in three weeks, according to Saints coach Dennis Allen.

Carr left Sunday's game against the Detroit Lions and the Saints' Week 10 game against the Minnesota Vikings to go into the concussion protocol but sustained other injuries in both of those games as well. Carr, who sprained the AC joint in his throwing shoulder in Week 3 against the Green Bay Packers, has been listed with shoulder injuries in all three games.

"There's something there that he's still working through. It's not something that keeps him from being able to play or be effective when he's playing. Pretty typical that when a guy has an injury, if he's getting any sort of treatment at all, that he's listed that way on the injury report," Allen said.

Allen said that Carr's shoulder appears to be OK after the Lions game but that Carr is being evaluated for a rib injury. The rib injury was initially described as a back injury when Carr left the game Sunday.

"We don't have all the results back on that, but the shoulder seems like it came out fine," Allen said. "We'll evaluate him as he goes throughout the week and see what his availability is."

Backup quarterback Jameis Winston would be the likely starter if Carr is unable to play against the Carolina Panthers on Sunday. Winston has come in for Carr in the three games Carr left while injured this season.

"Jameis, he does some good things. He's been a starter in our league," Allen said. "There's a reason why he's here as our backup. If Derek's not able to go, the plan right now would be that Jameis would be in there. We'll put a plan together that gives him an opportunity to have success."

The Saints also gave an update on the injured member of the chain crew who left Sunday's game on a stretcher.

Nick Piazza, the injured official, was transported to the hospital during the game after Saints running back Alvin Kamara stumbled into his leg at the end of a play. The Saints said Piazza will likely require surgery due to the collision.

"Mr. Piazza underwent MRI testing this morning and was seen at the hospital by an attending orthopedic doctor," the Saints said in a statement. "He suffered a dislocated knee and a fractured fibula. His blood vessels remain intact and he will likely undergo surgery next week. He appreciates the many well wishes and the continued care he continues to receive."