Grosjean had a small moment in Turn 6, which resulted in his Honda-powered Andretti Autosport entry to be caught by the surging Juncos Hollinger Racing Chevrolet of Ilott.
The British driver closed up to Grosjean and darted to the left for a move entering Turn 7, but the two hit flush wheel-to-wheel, which sent Ilott off course and through maze of dirt that wraps around the 12-turn, 1.964-mile road course.
“Yeah, I didn't see him,” Grosjean told Autosport. “I was looking on the right-hand side. It was a traffic jam. He went on the left and I'm sorry. I just didn't.
“I was looking right and he was left. I think it is what it is. I don't know why he tried to go through at that point, but I was struck by #27 [Kyle Kirkwood]. I didn't see him.”
Grosjean put down a session-most 30 laps, ending up 16th overall and 0.4808s behind pace-setter Scott McLaughlin’s mark of 58.1516s.
Ilott, who ended up 20th and 0.7155s behind, had a different view of the incident.
“I don't what he is doing,” Ilott said. “He was driving off the track at the time. I think he knew I was there for a whole lap and defended into the corner. I don't know. I'm not too bothered by it. It's just a bit stupid really.
Source: Autosport