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.

Monday will likely bring more information about the health of Penix's knee, but his availability for Atlanta's Week 12 game against the New Orleans Saints may be in doubt. If he is unable to play, Cousins would be the next man up.

The Falcons kept the veteran passer on their roster this season in part because they believe he offers a high floor as a backup quarterback.

"We'll go find out what Kirk does well this week," Morris said. "I'm sure he'll have some input on it, and so will Zac (Robinson). Those guys will work together, depending on what happens with Michael. And we'll be able to figure those things out when we get closer to practice on Wednesday."

In spot duty, Cousins completed six of his 14 pass attempts for 48 yards. There were multiple drops with Cousins delivering the ball, but he helped march the offense down the field late in the fourth quarter to potentially score a game-winning touchdown.

Those hopes were brought to an end on a third-and-4 from Carolina's 27-yard line with 26 seconds remaining in regulation when Cousins lofted a pass toward wide receiver Drake London, who was in single coverage down the left sideline. London had proven clutch all day long, leading the team with seven catches for 119 yards, but he couldn't deliver on the third-down play, which would be his last.

When the Falcons' offense took the field for overtime, London was not with them.

It was quickly announced he, too, had sustained a knee injury and was ruled out for the remainder of the game.

"It's the same report on Drake," Morris said. "Obviously, he left the game after that sluggo attempt in the end zone and wasn't able to return."

London has been the Falcons' most consistent receiver this season and ranked third among all wideouts with 810 yards at the conclusion of Sunday's early games. His six touchdown receptions are tied for fifth.

Rapoport reported some potentially positive news about London's health on Sunday night.

The fourth-year pro has earned a reputation for toughness and has battled through injuries throughout the season, but the severity of this particular one remains unclear.