NASCAR driver Kyle Larson will not race at Martinsville Speedway on Sunday, failing to get medical clearance after fainting during an autograph session.

The team said in a statement Sunday that Larson remains at Carolina's Medical Center in Charlotte, North Carolina, for more testing.

Regan Smith will replace Larson in the No. 42 Chevrolet at Martinsville.

The 2014 Sprint Cup rookie of the year and a budding star, Larson was initially checked out at Martinsville Memorial Hospital on Saturday after fainting at the Chevy Stage in the fan area, but doctors believed he should see a neurologist to be safe. So he flew back to Charlotte.

The team says, "Although all tests came back negative and Larson feels completely fine, the doctors felt he should be held for more testing."