Stewart's car struck the driver, 20-year-old Kevin Ward Jr., who was on foot on the track and gesturing toward Stewart after their cars collided in a sprint-car race at Canandaigua Motorsports Park in upstate New York on Saturday night.
A three-time NASCAR Sprint Cup Series champion, Stewart opted not to race Sunday in the Cup race in Watkins Glen, N.Y. Regan Smith was tapped to drive Stewart's No. 14 Chevrolet.
(Unlike NASCAR stock cars, sprint cars are smaller, open-wheel race cars. Their name is unrelated to NASCAR's Sprint Cup Series, which is named after the telecommunications company.)
Stewart already was in danger of missing this year's NASCAR Chase for the Cup, a 10-race playoff that starts Sept. 14.
Including Watkins Glen, there are five races left to determine the 16 drivers who will qualify for the Chase. Drivers who have won races during the regular season are virtually guaranteed a spot, followed by those highest in points.
Stewart, 43, does not have a win yet this season, is 19th in the Cup point standings and currently is outside the Chase field.
Watkins Glen International, a curvy road course, was thought to be one of Stewart's best chances of getting into the Chase with a victory. He already has five wins on the 2.45-mile track, the most of any Cup driver.
It's unclear whether Stewart will miss additional Cup races. Authorities in New York said no criminal charges were pending against Stewart, and it's unlikely NASCAR would take any immediate action because Saturday's race was not a NASCAR-sanctioned event.
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