"It's tough. I don't know what the future is going to hold for me," Best said via the Baltimore Sun. "It's been about a year and a half now, but I'm still working out like I'm playing next week."
Best has been symptom-free for more than a year now, but he can't find a neurologist willing to clear him for full-contact practices. He's been in the same holding pattern since last offseason.
Best is in Baltimore as the Lions' representative for the Ed Block Courage Awards that recognize players overcoming adversity. Though Best is under contract through the 2014 season, he's facing long odds to put on a Lions uniform again.
Still just 24 years old, Best will get another chance in the NFL if he can gain medical clearance in the next few years.
"I'm staying ready," Best said, "so if the opportunity does present itself, I'll be ready."
Follow Chris Wesseling on Twitter @ChrisWesseling