Rugby fans have been told not to go to Saturday's Wales game with South Africa if they are intent on causing trouble.
The Welsh Rugby Union is investigating complaints drunken fans abused a disabled man at Wales' defeat to New Zealand at the Principality Stadium.
Police and crime commissioner Alun Michael said Cardiff's reputation as a safe place to watch rugby could be damaged by continued bad behaviour.
Wales coach Robin McBryde has told potential troublemakers to stay away.
"For those who want to spoil it, don't bother coming at all," said the Welsh forwards coach.
The Principality Stadium is surrounded by pubs and bars in the heart of Cardiff city centre.
"It is a fantastic day out for the opposition, they love coming to Cardiff," said McBryde.
"There is no better stadium in the world. It would be a shame to spoil that because of the behaviour of one or two," he added.
But Mr Michael has said any more drunken behaviour from fans could increase the calls for alcohol to be banned inside the stadium.
Anyone travelling to Cardiff on Saturday is advised to arrive in ample time as the city is expected to be "very busy" with rugby fans and Christmas shoppers.
About 67,000 people are expected at the rugby game and stadium gates open at 11:30 GMT ahead of the 14:30 kick-off.
Supporters have been warned they could miss the start of the Springboks game if they do not arrive at the ground early to go through increased security checks as the UK's terror threat level is at severe.
The Principality Stadium is working with the Wales Extremism and Counter Terrorism Unit, although South Wales Police has stressed there is no specific threat to Cardiff.
Cardiff road closures
A full city centre road closure will begin in Cardiff from 11:00.
Rail companies are advising passengers to travel to Cardiff on the earliest possible service on Saturday, warning trains "will be busy all day".
There will be 12 extra high-speed mainline services to and from Cardiff, adding 6,000 seats, but upgrade work between Swindon and Didcot on Saturday means journeys from London will take about an hour longer.
Arriva Trains Wales will add extra capacity to Valley line trains and, after the match, customers for Cardiff and Valleys routes have been told to use Cardiff Queen Street station.
Buses will be diverted out of city centre bus stops and will terminate at either Churchill Way, Greyfriars Road or Tudor Street.
Cardiff Bus night services will be available on routes to Ely, Thornhill, St Mellons and Pontprennau until 03:30 on Sunday.
Meanwhile, the M4 westbound will be shut at Newport overnight on Saturday at 19:00.