TALLAHASSEE, Fla. -- Karlos Williams was projected as a defensive star when he arrived at Florida State as the No. 5 overall recruit in the nation in 2011, but Jimbo Fisher announced Thursday that Williams' future would be on offense.

Williams has worked the past two days at running back, Fisher said, and going forward, he expects the move to be permanent.

"He's 6-1, 232 pounds, runs a 10.5 100 meters, can catch, can run, is very natural with the ball in his hand, is physical, fast, learns," Fisher said. "He's doing a really nice job, and I think he can provide not just depth there, but he can drive some spark there."

Fisher said the move wasn't based on Williams' struggles at safety, where reviews of his play were tepid at best. When Lamarcus Joyner moved to cornerback this offseason, it was widely expected Williams would take over a starting job, but he was unable to lock down the spot on the depth chart during fall camp. Tyler Hunter started Monday's game at safety alongside Terrence Brooks.

Williams' high-water mark on defense came in an emergency stint at linebacker in last season's ACC championship game, in which he made 11 tackles and secured a game-clinching interception. He's also starred as a kick returner, but Fisher said he believes Williams' best chance to make a significant impact is at running back. It's a discussion Fisher said they've had before, but Williams finally agreed.

"It's what I think you can be, where I think your best future is and where you can help this football team," Fisher said. "But if you force somebody to do something they don't want to do, they're not going to be good at it."

Fisher said Williams worked at running back sparingly during fall camp, but he said the junior was "very enthusiastic" about the move.

Fisher said the move was necessitated in part because of a lack of depth at tailback. Redshirt freshman Mario Pender was ruled academically ineligible just before the start of the season, and junior James Wilder Jr. is dealing with a shoulder bruise. Fisher said he doesn't expect Wilder to miss time -- FSU is on a bye this week -- but he said Williams can provide a home run threat on offense.

"He's very natural with the ball in his hands," Fisher said, "and he can change numbers on the scoreboard."

Williams -- whose older brother Vince, a linebacker, was selected in the sixth round of this year's NFL draft by the Pittsburgh Steelers -- was a consensus five-star recruit as a safety, but he did occasionally get work at tailback in high school. He ran 69 times for 564 yards and seven touchdowns as a senior.