The Rams also released former first-round draft pick Vernon Gholston and veteran fullback Ovie Mughelli, sticking with incumbent Britt Miller. NFL teams had until 9 p.m. EDT to make moves.
Gholston, the No. 6 pick in the draft by the New York Jets, did not play in 2011. He was picked up earlier in the preseason to add depth to the defensive line.
Mughelli made the Pro Bowl in 2010 for Atlanta but was released in May to clear salary cap space and was coming off a knee injury in Week 7 last year. He signed a one-year contract with St. Louis last month.
Linebacker Aaron Brown, a seventh-round pick, was the team's lone draft selection to be cut.
Davis was impressive throughout the preseason after going undrafted out of Southern Mississippi. Davis and Clemens both struggled in the preseason finale, a 31-17 victory over the Ravens on Thursday night, with Clemens going 2 for 8 for 10 yards with an interception and Davis 1 for 4 for 13 yards.
Clemens played for offensive coordinator Brian Schottenheimer with the Jets.
Coach Jeff Fisher met with reporters three hours earlier and said then that the team was still in the process of finalizing cuts.
"I think we're in a good spot right now," Fisher said. "We're young, we still have a lot of work to do. You can get done a lot of work over the next 10 days prior to the start of the season, then we'll just have to focus on improving throughout the year.
"I think this is a team that's going to be fun to watch."
St. Louis also waived defensive tackle Cornell Banks, centers
Tim Barnes and T. Bob Hebert, quarterback Tom Brandstater, defensive ends
Mason Brodine, Jamaar Jarrett and Scott Smith, linebacker
Sammy Brown, defensive back Kendric Burney, tight ends Ben Guidugli,
Cory Harkey and Deangelo Peterson, wide receiver Nick Johnson, running back
Chase Reynolds, offensive tackles
Joe Long and Jose Valdez, and offensive guard Bryan Mattison.
"Like Detroit has us, we've been looking at Detroit for weeks," Fisher said. "We've looked at last year's Detroit and followed them through the preseason. So, the staff has a good feel for it. So, the next step is to translate to the players and create a situation the players can be successful."