Wales and Ospreys centre Gavin Henson was banned for 10 weeks and two days by a disciplinary panel on Friday.
That will see Henson miss the first three games of the RBS Six Nations, against England, Scotland and Ireland.
The 23-year-old was found guilty of elbowing Leicester prop Alejandro Moreno, but was cleared of kicking him.
Fellow Osprey and Wales squad member Ian Evans has been banned until 19 February for stamping on Harry Ellis in the same Heineken match last Sunday.
Friday's independent disciplinary committee was made up of chairman Rod McKenzie (Scottish Rugby Union), Dr Barry O'Driscoll (Irish Rugby Football Union) and Professor Lorne Crerar (SRU).
The Ospreys management can still appeal against the decision and appear likely to challenge the panel's findings.
Ospreys team manager Derwyn Jones said: "We are very disappointed with both verdicts, and we will now consider our position as to whether or not to appeal the sanctions imposed."
Any appeal hearing could conceivably result in Henson or Evans receiving an even longer ban, although the Ospreys would campaign for a considerable reduction.
Both players will miss several important Celtic League games, plus the Ospreys' final two Heineken Cup pool fixtures against Clermont Auvergne and Stade Francais in January - although the Welsh region cannot qualify for the European knock-out stage.
Evans, 21, was a surprise call-up to the Wales squad in the autumn following Brent Cockbain's injury, and sat on the bench for the Tests with South Africa and Australia.
But his eight week and two day ban rules him out of the first two Six Nations matches against England and Scotland.
His stamp at Ellis resulted in the England scrum-half having "a small operation" on his knee.
He had been cited by citing commissioner Bill Dunlop for kicking Ellis, but the European Rugby Cup disciplinary panel found him guilty of the lesser offence of stamping.
Henson was playing just his second game since recovering from his groin injury when he broke Moreno's nose with his elbow.
The centre's first opportunity to get back in action will be the Six Nations home match against Italy on 11 March.
However, Wales coach Mike Ruddock is unlikely to pick a player who is not match fit.
The controversial Liberty Stadium encounter followed a full-blooded encounter at Welford Road the previous week and a bitter build-up during which the Ospreys accused their opponents of cheating.
The war of words continued at the final whistle on Sunday with the Ospreys claiming Tigers forwards coach Richard Cockerill aimed a volley of abuse at the home dug-out.
"It was a disgrace," said Ospreys joint managing director Mike Cuddy. "There were children and other spectators within ear-shot but that did not stop him ranting and raving.
"There is always banter in rugby but this went beyond that. Leicester ought to be ashamed of themselves."