Philippe Saint-Andre has moved to defend Pascal Pape after the France lock was given a yellow card for kneeing Jamie Heaslip in the back in Ireland's 18-11 victory in Dublin.
France lock Pape was sin-binned for kneeing Heaslip in a ruck in the Six Nations encounter, with Ireland's No 8 now a serious injury doubt to face England on March 1 with back trouble.
Head coach Saint-Andre claimed his experienced lock's challenge was an accident, but conceded the second-half incident cost Les Bleus any chance of victory.
"When you watch the images of the incident I don't think you can say it was deliberate," said Saint-Andre.
"However, I said to Pascal you received a yellow card just at the moment we were gaining the upper hand both physically and territorially.
"Although we didn't concede many points it was still a pivotal moment. "You expect something like that from an inexperienced player, not one with over 50 Tests under his belt. It was the worst possible moment for that to happen."
Despite Saint-Andre's defence, Stade Francais lock Pape could still face a citing for the incident, even though referee Wayne Barnes ruled the challenge merited a yellow card rather than red.
Ireland boss Joe Schmidt admitted after Saturday's match that experienced loose-forward Heaslip was "very uncomfortable" following Pape's crude challenge to his back.
"He's very uncomfortable at the moment: he got a knee in the lower back," said Schmidt.
"So we'll get him checked out over the next couple of days."
Heaslip missed Ireland's 26-3 victory over Italy in Rome with shoulder and knee trouble, but returned in impressive fashion against France.
The 31-year-old was in obvious pain when he was removed on the hour in Ireland's gritty victory over Les Bleus, and Ireland bosses remain concerned over his chances of facing England in two weeks.
Former Toulon and Sale coach Saint-Andre also reacted angrily to criticism of playmaker Camille Lopez, calling on media to "stop picking on the fly-half".
SIX NATIONS: IRELAND v FRANCE