Dale Earnhardt Jr. has dropped out of Sunday's Sprint Cup race at the New Hampshire Motor Speedway due to symptoms of a concussion.
Earnhardt was evaluated in Charlotte, North Carolina, this week and doctors did not clear him to race. Hendrick Motorsports said on Thursday it had no timetable for his return.
Alex Bowman will drive in his place.
NASCAR's most popular driver, Earnhardt was involved in a 22-car wreck in Daytona earlier this month. He says he was feeling fine last week and thought the problem was allergies. When that didn't help, he met with a neurologist.
Earlier this year, Earnhardt pledged his brain to researchers looking into the connection between concussions and traumatic brain injuries.