London - Ulster number eight Nick Williams has been banned for eight weeks after being cited for striking Cardiff Blues' Wales international fullback Rhys Patchell, the Celtic League announced on Wednesday.
With the current season due to finish at the end of May, Williams will not be able to resume playing until September 1.
Williams was sin-binned for making illegal contact with Patchell's head at the breakdown in the first half of Ulster's 36-17 home win last Friday, which resulted in the Welshman being stretchered off and taken to hospital.
"The disciplinary committee ... found that the incident was at the top end of the World Rugby sanctions for this type of offence, meriting a 16-week starting point," the Celtic League said in a statement.
"In the absence of any aggravating factors and in light of several mitigating factors, including the player's exemplary previous playing record, the disciplinary committee applied an eight-week reduction from the entry point and suspended the player from playing for eight weeks.
"Taking into account the matches remaining this season, and two warm-up matches scheduled for the start of next season, Nick Williams is free to resume playing from September 1, and has the right of appeal."