LONG POND, Pa. -- Kurt Busch was not cleared by NASCAR's medical staff to compete in Sunday's race at Pocono Raceway, and the 23XI Racing driver was replaced by 19-year-old Ty Gibbs, who finished 16th in the race.
Busch, 43, who has hinted next season will be his last driving in NASCAR, tweeted he suffered from "concussion-like symptoms" from a hit suffered during Saturday's qualifying session.
"The tests indicate that I am still recovering," Busch wrote.
Busch, who has made 776 career Cup starts, is the 2004 series champion and is in his first season driving for a team co-owned by Michael Jordan and Denny Hamlin. His No. 45 Toyota spun on Saturday and slammed into NASCAR's protective safer barriers.
23XI selected Gibbs, grandson of Joe Gibbs Racing owner and former NFL coach Joe Gibbs, to make his first start. Gibbs finished second in Saturday's Xfinity Series race and is third in the series points standings.
Ty Gibbs said Sunday he had to pull over on the side of the highway and collect his thoughts when he got the call Saturday to replace Busch. Gibbs was already back in North Carolina and hopped on a racing simulator until 1 a.m. to get himself ready for his debut.
Gibbs has eight wins in 36 career Xfinity starts driving for a team owned by his grandfather.
"I'm very thankful just to come into this whole thing,'' he said at his hauler. "I did not expect it at all. It means a lot. I'm going to very disciplined in these situations.'' Gibbs also thanked Jordan for the opportunity -- "I always looked up to him'' -- but had not talked to NASCAR's most famous team owner.
The Associated Press contributed to this report.