ATLANTA — Leading 21-16 in the third quarter of Sunday’s game against the Carolina Panthers, Atlanta Falcons quarterback Michael Penix Jr. dropped back to pass on third-and-10 from his own 22-yard line. Under pressure, Penix quickly tossed an incomplete pass to his left as he was tackled to the ground.

When he rose to his feet, it was apparent that something was wrong.

Penix reached down to grab his knees before attempting to walk off the field. While on the way to the sideline, he lay back on the ground and tossed his helmet off. He was then attended to by trainers, who walked with him back to the bench and into the blue medical tent.

Shortly thereafter, it was announced Penix was questionable to return with a knee injury. He never did. Kirk Cousins entered the game and remained at quarterback until the final whistle.

Atlanta lost the game, 30-27, but it may have lost more than that — at least for the foreseeable future.

Falcons head coach Raheem Morris did not have an injury update on Penix during his postgame press conference.

“We’ve got to go see where the knee is and where he’s at,” Morris said.

Penix overcame two ACL tears while in college to become one of the league’s most prolific players while at the University of Washington. He wears a brace on his right knee for added protection.

In the immediate aftermath of the game, Morris said it was unclear exactly which knee his quarterback injured.

“I think it was the same knee that it was previous to this injury,” he said. “That wasn’t really the focus for me right there at the time. I can find out for you tomorrow.”

Before leaving the game, Penix was putting together one of his most efficient games as a pro. He was 13 of 16, including 11 of 12 in the first half, for 175 yards with no touchdowns or interceptions and a 112.2 passer rating.

After the game, NFL Network’s Ian Rapoport reported that Penix is believed to have aggravated the same knee that kept him out of Atlanta’s Week 8 loss to the Miami Dolphins.