Denny Hamlin was a late scratch from Sunday's NASCAR Sprint Cup race in Fontana due to a sinus infection that affected his vision, Hamlin's team announced.
Sam Hornish Jr. was tapped to replace Hamlin in his No. 11 Toyota prepared by Joe Gibbs Racing, team president J.D. Gibbs said.
The announcement came only 30 minutes before the start of the Auto Club 400 at Auto Club Speedway.
Hamlin had qualified to start 13th in the 43-car field. But under NASCAR rules, Hornish will have to start at the rear of the field due to the driver change.
This is the second consecutive year that Hamlin, 33, has found misfortune in Fontana.
At last year's race, a crash with Joey Logano on the last lap sent Hamlin's car hard into an inside wall. Hamlin suffered a compression fracture in his lower back and missed the next four races.