Police, supporters' groups and club management have urged troublemakers to stay away from the Swansea Cardiff football derby on Sunday week.
More than 30 arrests were made when the clubs met at the Liberty Stadium in September.
Police said they would have a "significant" presence to ensure that "genuine" fans enjoyed the game.
All those arrested last time would be kept away from the ground through banning orders or bail conditions.
Chief Supt Mark Mathias said: "We will have a significant amount of officers on duty and for those genuine supporters my officers will welcome you to the city and assist you in anyway possible.
"For those people, and I will not call them football supporters, who are thinking of turning up and causing the same violent scenes that we saw in September - the message is simple - stay away."
Mr Mathias said he was happy the police operation in September was a success as the rival fans were kept well apart and prevented from clashing.
"We don't want the small minority of idiots from both sides causing any trouble"
The police officer said most fans had behaved themselves and he thanked them for their help.
"The vast majority who turned up to watch the game did us a huge favour by not getting involved and walking away," he added.
Following September's match police issued CCTV footage of over 30 people they wanted to speak to, with ordinary fans helping to identify them.
'Dream fixture'
Swansea's manager Roberto Martinez said both clubs "enjoyed the passion" of derby matches and urged supporters to ensure that it was the football and not off-field events that made the headlines.
Cardiff assistant manager Terry Burton said: "I think we all want the same thing which is for supporters to enjoy the game - I know we are looking forward to it."
Both clubs' supporters' trusts have also appealed for troublemakers to stay away.
Vince Alm of the Cardiff City Supporters Trust praised police for the way the last match was handled and said at all times visiting fans felt safe.
"From the fans perspective it's the fixture we all dream about and we enjoy the passion.
"For fans to come and spoil these occasions - they can't call themselves football supporters.
"There are lots of women and children now coming to watch football - they are going to be the lifeblood of the game in the future - we don't want the small minority of idiots from both sides causing any trouble."
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