Though coach Hue Jackson talked around the injury Friday, the team confirmed the fracture after defensive coordinator Ray Horton said earlier in the day that McCown had a broken collarbone.
"I was probably most disappointed for Josh," Horton said of the 25-20 loss. "He went out there and played with a broken collarbone [and] until the last throw had a chance to win. We talk about the heritage of Ronnie Lott getting a finger amputated to play the game and how precious this game is and what guys will do to play in this game.
"And so, for me, it was disappointing that we didn't win it for Josh."
Jackson said the team considers McCown week-to-week. ESPN NFL Insider Adam Schefter has reported that McCown likely will miss multiple games.
"What's in there is in there," Jackson said.
McCown left for the locker room late in the first quarter to have his shoulder examined. He returned and finished the game, completing 20 of 33 passes for 260 yards with two touchdowns and two interceptions. He finished the game in obvious discomfort.
He missed the final five games of the 2015 season after breaking the collarbone, also against Baltimore.