McLaughlin had just taken what should have been his final pit stop when he rejoined just ahead of the #28 Andretti Autosport entry in the battle for the effective lead, for the second time that afternoon.
On cold tyres, he was forced to run a defensive line at Turn 4, but locked the rear brakes and made contact with Grosjean, putting the Frenchman into the tyre wall.
The pole-sitter was out on the spot while McLaughlin would finish 11th after serving a drive-through penalty over the incident.
The Team Penske driver admitted immediately post-race that he “need[s] to make better decisions” and sought out Grosjean to apologise, but now thinks it was a racing incident.
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He told the Pit Pass Indy Presented by Penske Truck Rental podcast, “I had done this pass before but I was on the green [alternate] tyre, I was now on the black [primary] tyre.
“I knew I was on a black tyre obviously but I made an error. I think if I didn't lock my rears towards the end of the braking, maybe I make the corner without contact; I think I make the corner.
“But at the same time, [Grosjean] was barely going to make the corner as well with how deep he threw it in. I think it's a racing incident.
“I'm sorry for my part in it, for sure, and that's what I probably apologised for probably more so.
“Looking back on it now, I probably took more of the blame than I probably should have, but I'd rather that way because that's just how I saw it firsthand.
“Captain hindsight's a wonderful thing, you can look at it many different ways, from different angles and whatever and come to the conclusion about whoever's at fault.
“But, looking back on it now, I definitely think probably it was a racing incident, and I think Romain got that, but I'm glad I took it on the chin and got on with it.
“It's one of those deals; I wasn't going to back out, I'm racing to win. If it was second-last race of the year [and] I needed points, yeah, probably would have thought about it a bit more.
“But I knew if I got past Grosjean there, we would have won the race, there's no doubt.”
McLaughlin was, however, left frustrated by a gamble on the overcut which went wrong and set the incident in train.
Grosjean was tailing Car #3 when he was called into the pits at the end of Lap 70, whereas the New Zealander's crew left him out a lap longer.
During that extra 1.8mi (2.9km), McLaughlin caught traffic which cost him precious time and thus he exited just ahead of Car #28.
“It sucks that I took another driver out with me, but at the same time, I was more pissed off with my team, and the opportunity that we had,” he revealed.
“It was just disappointing because I knew that we did get held up coming in.
“I wish I got held up a little bit more so I wasn't even in that position. It was just like the most awkward position we could have been in and it made us having to make that split-second decision.
“But, like I said, hindsight's a wonderful thing, it is, but for us to still finish the race, get out, and I think we're 11th in the points now, I think we were very lucky.”
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