The Team Penske driver was trailing Colton Herta by almost three seconds, late in the first stint, when he locked up and slid into the tyre wall at Turn 1 on Lap 33.
He was heard simply saying “Sorry” on his radio as the incident triggered the third Caution of the afternoon.
Whether or not light rain was a factor is not clear.
McLaughlin is going again and, while he initially dropped a lap, the intensification of the rain could force a switch to wets and effectively give him the chance to take a free pass.