The extent of the injury to Bradford's left knee was confirmed after an MRI exam, the team said Monday. Coach Jeff Fisher was to provide details later in the day at his regular news conference.
Bradford tore his anterior cruciate ligament in the fourth quarter of Sunday's 30-15 loss to the Carolina Panthers when he landed on his knee after being shoved out of bounds by Panthers safety Mike Mitchell. Fisher said after the game that Bradford was in "significant pain" on the sideline.
Kellen Clemens replaced Bradford and is the only other quarterback on the roster. The Rams' next game is next Monday night at home against Seattle
Bradford threw for 255 yards and a score Sunday, with one interception and two sacks as the Rams dropped to 3-4.
Bradford, the No. 1 pick in the 2010 draft, has thrown for 1,687 yards with 14 touchdowns and four interceptions this season. St. Louis had won its previous two games, with Bradford throwing three TD passes in each. Bradford had season-ending shoulder surgery in 2009 when he was at Oklahoma
"It's never easy when you see a teammate go down," Clemens said after the game. "When you see a person that you spend as much time with as I do with Sam and genuinely care about as a person. ... I have great respect for what he does on the field, but just as genuine concern for him as a person."
Added center Scott Wells: "Even if Sam wasn't hurt, we still have some heavy lifting to do. But this adds extra to it."