Richie Rees is set to miss the whole of Wales' Six Nations campaign after being handed a 12-week ban for making contact with the eye of Dylan Hartley.
An independent European Rugby Cup disciplinary panel decided on the punishment for the offence, which occurred during Cardiff's Heineken Cup clash with Northampton.
Blues' scrum-half Rees appeared before the hearing on Thursday after a citing complaint arising from the Heineken Cup Pool One match at Cardiff City Stadium on December 19.
Rees pleaded not guilty to the complaint, which was for acts contrary to good sportsmanship in contravention of law 10.4(m), but was found guilty after judicial officer Pat Barriscale reviewed the evidence, including television replays and medical reports.
An ERC statement read: "The judicial officer determined that Mr Rees was guilty of foul play in contravention of Law 10.4(m) in that he had made contact with the eye/eye area of Mr Hartley.
"The judicial officer found that the contact had been reckless and not intentional.
"The judicial officer found that the offending was at the low end of the level of seriousness for an offence of this type, and having taken into account all aggravating and mitigating factors imposed a suspension of 12 weeks.
"Mr Rees is free to play again on 31 March, 2011."
Rees established himself in the Wales set-up over the course of 2010 after making his international debut against England in that year's Six Nations.