Racing Metro centre Fabrice Estebanez has been banned for four weeks for striking Saracens winger David Strettle.
Estebanez, who has eight France caps, was found guilty of the incident during a Heineken Cup clash between the sides last weekend when he appeared at a disciplinary hearing in Dublin.
He cannot play again until 11 February and will miss Racing's Heineken clash against Munster in Limerick on Sunday.
England star Strettle was carried off following the third-minute incident in Nantes, although he has now recovered and is in contention for Saracens' final group game against Edinburgh on Sunday.
In a statement, European Rugby Cup said: "The judicial officer upheld the complaint and found that Estebanez had committed a reckless act.
"He determined that the act was in the mid range (five weeks) of the IRB (International Rugby Board)'s sanctioning regime, and taking into account the limited mitigating factors of the player's remorse and good conduct during the hearing, the judicial officer reduced the suspension by one week."
Stade Francais player Juan Cruz Guillemain, who also appeared at the Dublin hearings, was banned for five weeks.
Guillemain was cited for striking Grenoble player Fabien Alexandre with his head during last Saturday's Amlin Challenge Cup game between the clubs - he is banned until 18 February.
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