THOUSAND OAKS, Calif. (AP) Los Angeles Rams cornerback Troy Hill's surprising start made free-agent signing Coty Sensabaugh expendable after just four games.

With Trumaine Johnson unlikely to play against the Detroit Lions this Sunday, Hill will again be called upon to fill a bigger role than was initially expected of him.

Coach Jeff Fisher said Tuesday that Johnson is ''probably not going to go this week.'' Johnson, who hurt his right ankle in the fourth quarter of the Rams' 30-19 loss to the Buffalo Bills, left the locker room in a walking boot using a crutch for support.

''He'll be week-to-week,'' Fisher said.

That puts Hill in line to make his third career start against the Lions. Hill made two starts earlier this season when E.J. Gaines was dealing with a thigh injury, making a career-high 11 tackles in the victory over the Tampa Bay Buccaneers.

Fisher is impressed with Hill's willingness to stop the run despite only weighing 182 pounds. Hill can also elevate to play the ball, allowing him to deal with bigger receivers in spite of his 5-foot-10 frame.

''He hasn't had that many snaps but he competes, and that's all you can ask for,'' safety T.J. McDonald said.

If Lions quarterback Matthew Stafford plans on picking on Hill, it won't come as a surprise to the former Oregon Duck. Hill played opposite All-American Ifo Ekpre-Olomu in college and is used to being targeted frequently.

''You just got to expect it, especially when you ain't the big-time corner and you ain't got a lot of experience,'' Hill said. ''Every play I'm out there I got to expect the ball coming to me, so I got to be on my game every play, every single play. It just makes you a lot more hungry to make the plays to prove yourself. That's all I am looking for.''

For an undrafted player who spent last season on the practice squad of the Cincinnati Bengals and New England Patriots before appearing in three games with the Bengals, Hill isn't fazed by the prospect of facing the NFL's leading receiver in Marvin Jones.

Hill practiced against Jones when both were with the Bengals, giving him familiarity with what the replacement for Calvin Johnson as Stafford's go-to option can do.

''I know what kind of receiver he is,'' Hill said. ''Explosive and he has got a couple moves, so just got to stay focused.''

To bolster depth in the secondary after releasing Sensabaugh, who signed with the New York Giants, the Rams claimed Dwayne Gratz off waivers Tuesday after the four-year veteran was cut by the Jacksonville Jaguars.

Rookie defensive end Morgan Fox was waived in a corresponding roster move.

Fisher said he liked Gratz coming out of college at Connecticut, and with the Rams preparing to travel to London immediately after the game against the Lions, it didn't hurt that Gratz's final game with the Jaguars was at Wembley Stadium earlier this month.

''Don't have to ask him if he had a passport or not,'' Fisher said.