Connacht coach Andy Friend said prop Dominic Robertson-McCoy is "really disappointed with himself" after he received a red card for an ugly stamp to Josh van der Flier's head on Saturday evening.
Robertson-McCoy walked 69 minutes into the visitors' 20-3 victory at the Sportsground, and Friend had no complaints.
"That wasn't good and Dom is really disappointed with himself," he told RTÉ Sport.
"He's actually a very decent man and it's certainly not in his nature. He put his boot in a position it shouldn't have gone and he paid the consequences."
Second-half tries from Garry Ringrose and Sean Cronin gave Leinster a gritty and deserved win in Galway.
Connacht have shown some real promise in the early days of Friend's reign and brought massive physicality to their clash with the reigning Pro14 and Champions Cup holders. But ultimately Leo Cullen's side had too much nous.
"It was a good lesson," Friend added. "They are quality. There's no let-up. We said it before the game, we looked at the team they presented and we said, 'that's great'. We were grateful for that because you only get better when you play better opposition.
"I just loved our energy. We never stopped. There's a great spirit within this group. We've got some areas we need to tidy up, we know that, but you can never doubt these boys' heart and desire. They didn't stop trying and they wont stop trying. We'll jeep getting better."
