Former France number eight Sébastian Chabal is almost certain to be suspended after knocking out Agen's Marc Giraud.
Chabal, playing for Lyon in the ProD2, delivered the punch after being held onto by Giraud at the back of a ruck. Remarkably he was only shown a yellow card.
The 36-year-old former Sale Sharks and Racing Métro player won 62 caps for France and has always been renowned for his aggressive play on the field.
Chabal is set to retire at the end of the season but may now receive a heavy suspension after knocking Giraud unconscious.
Agen president Alain Tingaud was understandably upset with the decision not to show Chabal a straight red card.
"I am furious with the referee who did not show a red card. He admitted he made a mistake. It was a red," said Tingaud.
Suspensions for striking an opponent range from two to 52 weeks. Watch the footage below: