The Lions learned Monday that running back
"After today's consultation with medical experts, including representatives from our medical and training staffs, it has been determined that Jahvid will not be permitted to return to play at this time," Lions General Manager Martin Mayhew said in a statement.
"Throughout this entire process we always have placed the highest priority on what is best for Jahvid from a health and safety standpoint," Mayhew continued.
"While today's decision is disappointing from a football perspective, we fully and entirely respect and support this recommendation."
Best said last week he wouldn't consider retirement if he wasn't cleared for a return, though.
"No," he said. "Then we'll have to sit back down and have more discussions and see where we can go from there."
Mayhew affirmed those remarks in his statement today.
"Jahvid will continue to work with our medical and training staffs with the hope that he ultimately will be cleared to return to the playing field," he said.
Though it doesn't appear that will be this season after his latest setback, the window hasn't closed yet, according to Lions head coach Jim Schwartz.
"There's still time," he said in an interview on the Lions Review Show on 97.1 The Ticket. "We don't have to activate him from PUP yet, there's still a couple more weeks and then there's a three-week practice window, so that time hasn't run out."
The sands in the hourglass are getting pretty low, though.
Tuesday will be one year to the day since Best suffered his most recent concussion in a Week 6 loss to the 49ers. It's uncertain how much can really change in a matter of weeks when it hasn't changed over the course of the last year.
Best previously went through the protocol to try and return to the field three months prior to last week's tests, with the same result: no clearance.
"It's nothing that we can control. We move on," Schwartz said. "You can't worry about what you don't have. You have to worry about what you do have and make the best of it. We have to prepare to play Chicago without him."
Best said in the offseason the concussion he suffered against the 49ers last season was the third of his career.
He suffered one against the Browns in the preseason last year and a devastating one that ended his college career at Cal. The one he suffered in college against Oregon State was the only one in which he was knocked unconscious, he said.
In the locker room last week, Best told reporters he was in the top physical condition of his life and hadn't had a symptom in "months."
Only Best, the Lions front office and his medical team know exactly what's preventing him from returning to the field.
Best cited "personal reasons" for not wanting to get into any specifics about his case when talking to reporters, saying each case was unique, but he seemed optimistic he'd get clearance to return.
This is a big blow to a Lions offense that has yet to have an "explosive" run play (20 yards or more) this season. Best is a big-play threat and probably the second-best mismatch they can utilize outside of receiver
In 22 career games, Best has rushed for 945 yards with six touchdowns. He also has 774 receiving yards and three more touchdowns.