Detroit Lions running back Jahvid Best, who has not played since suffering another concussion last October, likely will start this season on the physically unable to perform list and miss at least the first six games, according to a source familiar with the situation.
Doctors still have not cleared Best to play, a surprise to some Lions officials but evidence of how carefully Detroit is bringing him along.
The 23-year-old Best and the Lions have received different opinions from different doctors, but the team does not want to rush him back to action. 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.
The Lions also will be without running back Mikel Leshoure, who has been suspended the first two games for violating the NFL's substance-abuse policy. Leshoure returned to practice Wednesday after missing most of training camp to recover from a right hamstring injury. He participated during individual drills and then did some conditioning work.
Detroit drafted Leshoure in the second round last year out of Illinois, but he hasn't played a down for the Lions. He missed all of his rookie season last year with a torn left Achilles tendon.
Leshoure isn't expected to play in Friday night's preseason game at Baltimore, and it's unclear what his timetable might be to participate fully in practice.
"He's been running on the side. He's been making good progress," Lions coach Jim Schwartz said. "Last week he was able to run a little bit, and it got a little bit sore on him after that, delayed us a couple days. But it's all just part of it."
Leshoure feels he can hit the ground running soon enough.
"It's probably one of the easiest positions to transfer from college to the NFL, because it's just running the ball," he said. "Protection is probably the hardest thing a running back needs to learn, but I've been here for a whole year and I've been learning since last year."
Information from The Associated Press was used in this report.