Overview
- Christopher Bell passed Kyle Larson in the closing laps to win the Cook Out Southern 500 after a late rain caution and red flag produced split pit calls on older versus fresh tires.
- Saturday practice and qualifying at Darlington were cancelled because of persistent lightning, so NASCAR set the starting order by its performance metric with Tyler Reddick on pole.
- Denny Hamlin was nudged by Michael McDowell late, reported toe-link damage, fell a lap down for repairs and recovered to finish 18th while retaining the Chase points lead.
- William Byron suffered a late engine failure and recorded a 37th-place DNF, which dropped him to last in the 16-driver Chase standings.
- Bell’s win vaulted him to second in the Chase, produced a Toyota sweep of the top three, tightened the standings and leaves teams focused on tire strategy and setup as the series moves to Gateway next weekend.