Another shot at NFL job for Trent Richardson?

Trent Richardson was traded from the Browns to the Colts and has since found himself out of the league.

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ORCHARD PARK, N.Y. (AP) — The Buffalo Bills’ depth at running back could be further depleted after tests revealed rookie Karlos Williams sustained a concussion.

General manager Doug Whaley disclosed Williams’ injury Tuesday during his radio show on Buffalo’s WGR-AM. Whaley says tests showed the concussion on Monday, a day after Williams complained of not feeling well following a 24-10 loss to the New York Giants.

Williams is following the NFL’s concussion protocol, and must pass a series of tests before being cleared to play. Buffalo (2-2) plays at Tennessee (1-2) on Sunday.

Williams was hurt after making his first start filling in for LeSean McCoy, who is out indefinitely because of a hamstring injury.

The Bills have only two other running backs on their roster, Boobie Dixon and Cierre Wood, plus fullback Jerome Felton.

A person familiar with the situation told The Associated Press that Trent Richardson and Alfonso Smith were among the free-agent running backs the Bills worked out at their facility on Tuesday. The person spoke on the condition of anonymity because the Bills did not reveal what players they brought in for workouts.

Richardson’s stock has dropped since being selected by Cleveland with the third pick in the 2012 NFL draft. After a solid rookie season, Richardson was traded to Indianapolis a few weeks into the 2013 season.

Richardson eventually lost his starting job with the Colts and has yet to find a job since being waived in March.

Smith has five seasons of NFL experience and spent last year in San Francisco, where he played under Bills new offensive coordinator Greg Roman.

Whaley also didn’t rule out the possibility of re-signing Bryce Brown, who was released on Sept. 15.