Kurt Busch will miss his fourth straight race due to concussion-like symptoms on Sunday in Richmond, Va.
Busch was injured during a qualifying crash at Pocono Raceway on July 23 and missed the following day's race. He also sat out Indianapolis Motor Speedway's road course and again at Michigan International Speedway last Sunday.
"Brain injury recovery doesn't always take a linear path," Busch wrote Wednesday on Twitter. "I've been feeling well in my recovery, but this week I pushed to get my heart rate and body in a race simulation type environment and it's clear I'm not ready to be back in the race car."
"This was by far the hardest week emotionally because I do feel the progression of recovery, but racing requires an extreme physical and mental effort and my body is not 100 percent able to sustain the intense race conditions."
"I am making progress and pushing hard each day. I am encouraged by my team of doctors, and we will continue to do everything it takes to get me to 100 percent to return to competition."
Xfinity Series driver Ty Gibbs once again will replace Busch in the No. 45 car for 23XI Racing. The 19-year-old Gibbs is the grandson of NASCAR owner Joe Gibbs.
Busch, 44, is in the midst of his 22nd full-time season as a NASCAR driver. He was the series racing champion in 2004 and won the Daytona 500 in 2017.
--Field Level Media