Detroit Lions running back Jahvid Best, who hasn't played since suffering his last concussion Oct. 16, 2011, will be undergoing a battery of tests this week to determine whether the Lions will activate him off the physically unable to perform list, according to sources.

Best has been seeing multiple doctors, and there will have to be a consensus from them before he's cleared to return.

Best is said to be in the best shape of his career, and the team is hopeful it will have him back for the game on Monday night, Oct. 22 against the Chicago Bears.

Best still hasn't received medical clearance, however, and the team refuses to guess whether or not he will.

Best suffered at least two concussions last year, one in the preseason and another against the San Francisco 49ers on Oct. 16. Best also suffered at least one significant concussion during his last college season at California, and some NFL teams took the running back off their draft boards because of concerns about his brain injury.