BEREA, Ohio -- Quarterback Johnny Manziel was diagnosed with a concussion and placed in the league's protocol Wednesday, putting his status for the Cleveland Browns' season finale against the Pittsburgh Steelers in doubt.
Austin Davis would be in line to start for the Browns if Manziel cannot play.
The Browns said Wednesday they don't know when Manziel was injured, but coach Mike Pettine said Manziel took a "pretty good shot" in Sunday's loss to Kansas City.
"We'll take a very conservative approach with it," Pettine said before the team announced Manziel's diagnosis.
Pettine said the team would decide about adding another quarterback for Sunday in time. If Davis is the starter, the team would either use Terrelle Pryor as the backup or sign another QB.
Pettine said Manziel will definitely start if cleared.
A video that appeared during the Christmas break showing Manziel partying would not affect Manziel's status for the game, Pettine said.
"He was at home on his day off," Pettine said. "As far as the judgment of it getting out there, I question that."
Pettine added that when a similar video, which showed Manziel partying during the team's bye week, appeared earlier in the season and contributed to Manziel's demotion, the real issue was that he was not truthful about what had happened. Pettine said he had not had the opportunity yet to speak to Manziel personally about the new video.
The Browns announced Wednesday that cornerback Tramon Williams has been placed in the concussion protocol, and it's highly unlikely he will face the Steelers on Sunday.
That means the Browns will face Pittsburgh without Williams and fellow cornerback Joe Haden, who is on injured reserve after being diagnosed with two concussions this season.
Information from ESPN's Pat McManamon was used in this report.