Regan Smith will replace Kyle Larson in the No. 42 Chip Ganassi Racing with Felix Sabates Chevrolet in Sunday's STP 500 at Martinsville Speedway as Larson is held out for additional tests following a fainting spell Saturday.
Larson fell ill during an autograph session at his merchandise hauler, and he was transported to a local hospital.
The team tweeted a statement Sunday morning, announcing the driver change: "Kyle Larson was evaluated & all tests came back negative. Larson feels completely fine, but doctors felt he should be held for more testing.
"Subsequently, Larson will be unable to race today in the #STP500. Regan Smith will fill-in for Larson today in the No. 42 Target Chevy."
Since he took part in Coors Light Pole Qualifying on Friday, qualifying seventh, Larson will remain eligible for the Chase for the NASCAR Sprint Cup should he meet the remaining eligibility requirements.