St. Louis Rams cornerback E.J. Gaines will miss the entire season with a foot injury, depriving the secondary of a probable starter.

Coach Jeff Fisher confirmed Gaines' injury and recovery period Monday after the team opened three days of workouts in Southern California. Fisher also expressed confidence that the Rams can fill the void with the players already on their roster.

Gained started 15 games as a rookie last season, getting two interceptions and finishing fourth on the Rams with 105 tackles. The Missouri product even held on to his starting job when incumbent starter Trumaine Johnson returned from a preseason knee injury.

"To come in as a sixth-round pick and get an opportunity because of injury and keep the job, I thought it was a very impressive effort last year by him," Fisher said. "We were counting on him. We were going to create competition between Trumaine and he this year and see what happens, and it's just unfortunate. He'll be back 100 percent. It's just not any time this year."

Gaines was hurt when his foot was stepped on during the first weekend of training camp on Aug. 2. He required surgery after developing a Lisfranc injury to the small bones at the top of his foot.

Gaines was expected to compete with Johnson for the starting cornerback spot opposite Janoris Jenkins. Johnson will step back into the first-string job, which he held for 12 games in 2013.

Fisher isn't worried about his secondary even though the Rams didn't draft a defensive back last spring. Lamarcus Joyner, a second-round pick in 2014, is expected to be St. Louis' nickel defensive back, while Marcus Roberson is ahead in the race to be the fourth cornerback.

Undrafted rookie Imoan Claiborne also is showing promise in camp, highlighted by his interception in the Rams' preseason-opening loss at Oakland last Friday.

"Tru is off to a great start," Fisher said. "Marcus is playing well, and LaMarcus also is doing a good job for us, and Jenks is Jenks. We've got a good group, fortunately."