The 32-year-old Grosjean, now driving for Haas, collided with Nico Hulkenberg and Pierre Gasly after losing control of his auto during the opening lap of the race in Barcelona, which was ultimately won by Mercedes' Lewis Hamilton.
"If you look at the footage, I had wanted to avoid contact with my team-mate". "I'm sorry for the others that were involved - there wasn't much I could do once the auto went".
"I don't remember an incident like it and I don't think the stewards did either - which is why they have given him a three-place penalty at the Monaco Grand Prix". Kevin had a bit of a wobble, I lifted off the throttle, and then the vehicle just went.
Haas boss Guenther Steiner was mid-way through his media session with written media when the decision came through.
Palmer then revealed that he had a personal incident with Grosjean when the pair crashed into each other during the Sochi GP a year ago.
"Obviously, Q3 could've been better and I'm not super happy to start P10 but, in general, I think we're in a good position for the race and I'm happy for the team".
Palmer continued: "Grosjean has the speed to get brilliant results on his day, and there's plenty of time for him to turn it around yet".
"If he had stood still, we don't know, maybe he would have knocked five out".
The statement on the decision said: "The driver stated to the Stewards that he made the decision to cross the track, trying to avoid the other cars and that he felt this was his best option".
"It's never a good place to be, in the middle, whatever you do - that's my point of view".
"I feel sorry for them that they were taken out but he didn't try an overtaking maneuver to take them out or understeer into anything".
Speaking ahead of today's race, Grosjean, who began in 10th position on the grid, said: "Pretty good qualifying for the team - both cars in the top-10".
"I lost the rear end of the vehicle and I tried to put it back as long as I could but it just didn't work", he told Sky F1.
"At the time Romain's biggest complaint was that I kept the throttle on as I was spinning and didn't just hit the brakes, which he saw as the reason he was collected and pitched into the wall".
The spin Grosjean had was one thing. I tried to stay on the throttle to spin it to try not and face other people.
But first I think he needs to clear his head and reset.
"It's a human reflex if you look at Rosberg in 2016 and Schumacher in 2010. Unfortunately once the auto started going forwards again onto the track, it was very hard".
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