Rush was sent off in the 55th minute against Northampton
Cardiff Blues number eight Xavier Rush has been suspended for one week after a red card against Northampton and will miss the Newport Gwent Dragons match.
Referee Jerome Garces red-carded Rush for a high tackle on Courtney Lawes in the Heineken Cup loss on Sunday.
Rush's suspension lasts "up to and including 27 December", the day on which the Blues travel to face the Dragons in the Magners League.
A hearing date is yet to be set for Blues scrum-half Richie Rees.
He was cited for allegedly making contact with the eye area of Saints' Dylan Hartley.
Rush could have faced a suspension of anything between two and 52 weeks for his tackle on Lawes, but will now be available for the home match against the Ospreys on 31 December.
Xavier Rush is not a dirty player and we felt the sending-off was quite harsh
Cardiff Blues director of rugby
"The independent judicial officer found it was a recklessly effected tackle with no intent by Mr Rush to make contact as high as he did," said a statement from the disciplinary hearing.
"There was also no intent to cause injury, and Mr Lawes appeared to almost be on one knee at the time of impact.
"The independent judicial officer considered there were no aggravating factors and he accepted that Mr Rush pleaded guilty, that he had an excellent record, that he showed remorse and that he conducted himself well at the hearing."
Blues director of rugby David Young felt his squad could cope with Rush's short-term absence.
"We have got cover in the back row with Tom Brown, Andries Pretorius and Maama Molitika able to play at number eight but obviously we want to go into the festive derbies with our best players," he said.
"Xavier Rush is not a dirty player and we felt the sending-off was quite harsh. It's good news that he will be available for selection for our match against the Ospreys on New Year's Eve."
Rees has been charged under law 10.4(m): "Contact with the eye/eye area; Acts contrary to good sportsmanship."
That is a more serious offence than the one committed by Rush, carrying a suspension punishment of between 12 and 156 weeks.
If found guilty of gouging, even a ban on the lower end of the scale would rule Rees out of most of Wales' RBS Six Nations campaign.