Robson is shown a red card in the opening minute of the season
Harlequins lock George Robson has been accused of breaking the spirit of rugby after head-butting Joe Simpson just 46 seconds into the 26-15 defeat by Wasps.
Robson, who was shown a straight red card by referee Dean Richards, later apologised to Simpson.
But the Wasps scrum-half, who sustained a headache and cut nose, said: "I am frustrated and disappointed. It is not the spirit of rugby."
Quins are still reeling following the 'Bloodgate' affair of the summer.
The west London club were always going to be under the microscope in their opening match of the Premiership season after being found guilty of using fake blood capsules in an attempt to cheat their way to victory in last season's Heineken Cup quarter-final against Leinster.
Coach Dean Richards was banned for three years and physio Steph Brennan suspended for two years for their part in ordering wing Tom Williams to feign injury to allow kicker Nicky Evans back on the field.
Harlequins' new head coach John Kingston refused to comment on the apparent head-butting incident, however, saying: "I will do an Arsene Wenger [Arsenal manager] and not make a comment from watching it live.
"George is upset. I spoke very briefly to him. He said sorry to me and he wasn't quite sure how it had all evolved.
"His sorry reflected the circumstances. I don't think it should be taken as a question of whether he had done something wrong.
"We will look and see what the pictures show and reflect on it."
However, Simpson said: "I am pretty sure that he head-butted me - I think the video will show everyone what they want to see.
"He tackled me after the ball. I was desperately trying to pull myself away and get to the next breakdown.
"He hung onto me. I thought I was ready to run off and then things happened. I was surprised by it. I wasn't expecting it at all. I have got a bit of a headache and I am still a bit wobbly."
Wasps director of rugby Tony Hanks insisted that the referee had no option but to send Robson off if he felt there had been a head-butt.
"I can honestly say I didn't see it but Joe Simpson's nose looks like there was a head-butt," he said.
Robson now faces being banned for at least a month.