Bradford has a high left ankle sprain and is in a walking boot, leaving his status for this week's game at Dallas in question.
"I think you are always concerned when you see your quarterback in a boot," Rams coach Steve Spagnuolo said. "In my experience with the high ankle sprains, you just never know."
Bradford was injured during winless St. Louis' 24-3 loss at Green Bay on Sunday, and Spagnuolo said he had a noticeable limp when he reported for a team meeting Monday afternoon.
The only consolation for St. Louis (0-5) is Bradford's plant foot is his right one, which could help him get back on the field sooner.
Backup A.J. Feeley likely will take the majority of the snaps with the first team when the Rams return to practice on Wednesday. The 34-year-old Feeley didn't get any game snaps last year and is 1 for 5 for 21 yards this year in mopup duty. The Rams likely will elevate Tim Brandstater from the practice squad.
"Oh yeah, A.J. will be ready," Spagnuolo said. "We'll be ready for any possible situation. That's why A.J. is here and I'm glad we've got him. He's been through this before."
Feeley, in his 11th season, said he's up for the challenge.
"It's the nature of the game," Feeley said. "Do I want to play? Yes. I've got that fire. I'm definitely excited about it."
Bradford was sacked 21 times in the first five games.
Bradford or Feeley could have a new veteran receiver to throw to on Sunday.
The Rams acquired Lloyd from the Denver Broncos in exchange for a 2012 sixth-round draft pick on Monday. They are hoping Lloyd can make an immediate impact given he's being reunited with offensive coordinator Josh McDaniels and playing in the same system.
"There shouldn't be any kind of a learning curve," general manager Billy Devaney said. "It's up to him and the coaches to see how quickly he gets out there."
Spagnuolo remembers Lloyd impacting the game plan in last year's game at Denver.
"We had to be aware of where he was and change some things coverage-wise," Spagnuolo said. "So that probably speaks volumes right there."
The Rams made room for Lloyd by releasing Mike Sims-Walker, a disappointment after getting a free-agent deal in August. Sims-Walker, who was inactive on Sunday, had six catches against the Giants in Week 2 but dropped two passes in Week 4 against the Redskins, and totaled 11 receptions with a 12.6-yard average and no touchdowns.
Danny Amendola, who led the team in receiving last year, is on injured reserve after dislocating his left elbow in the opener.
"Those two guys have really worked their butts off, but you don't really know until you get into the real game," Spagnuolo said. "The hard thing is going to be simulating that to find out where they're at."