Cleveland Browns' RG3 could now miss at least 12 weeks

Cleveland Browns quarterback Robert Griffin III is now expected to miss 10 to 12 weeks, possibly ending his season, sources told ESPN's Adam Schefter.

The Browns placed Griffin on injured reserve Monday after he suffered a fractured bone in his left shoulder in Cleveland's season-opening 29-10 loss against the Philadelphia Eagles.

Under the new injured reserve rules, each team can designate one player to return. Designation does not need to be made until that player is able to return to practice. A player placed on IR is eligible to return to practice in six weeks and must miss a minimum of eight games.

Griffin, who signed a two-year, $15 million contract with the Browns this offseason, completed 12 of 26 passes for 190 yards and one interception in Week 1.

Griffin said after the game he thought he had suffered a sprained shoulder, but medical tests revealed the fractured bone in his shoulder. RG3 was hurt when he was hit by Eagles cornerback Jalen Mills at the end of an 11-yard run with 3:41 left and the Browns down 22-10.

Veteran Josh McCown will start Sunday's home opener against the Baltimore Ravens. He started eight games for the Browns last season, completing 186 of 292 passes for 2,109 yards with 12 touchdowns and four interceptions.