Cardiff boss Neil Warnock has cited the sending-off of France rugby union lock Sebastien Vahaamahina as to why his team must stay cool against Swansea.
Vahaamahina was sent-off for an elbow on Wales' Aaron Wainwright in the World Cup quarter-final with France.
Warnock says his biggest fear ahead of Sunday's south Wales derby at the Liberty Stadium is a loss of discipline in the hostile atmosphere.
"You have to remind players not to lose your head," Warnock said.
"That is the big fear I have had in derby matches, somebody doing something that is totally out of character for them because of the atmosphere.
"You can get carried away with the atmosphere and forget what you are supposed to be doing."
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Les Bleus lock Vahaamahina was dismissed after 48 minutes at a time when France were leading 19-10 in Oita.
Wales scored 10 unanswered points to win 20-19 and Warnock said Vahaamahina's red card proved costly.
"You talk about discipline. The French lad will never be forgiven really. I think they would have won that game if he had not got sent off," Warnock added.
"It just shows you how disciplined you have to be in these big games, in these big moments in time.
"He will be remembered for that for the rest of his life unfortunately. I just thought they were superb until he got sent off.
"It just shows you that one bit of indiscipline and the whole team, the whole country have been kicked in the teeth.
"All credit to Wales for taking advantage of that, but you don't want to be remembered for something like that.
"It is quite easy with all the cameras, with all the media coverage and all the expectations, to forget your responsibilities. I will be reminding them of that. It is hard enough with 11 players, let alone 10."
Warnock knows none of his Cardiff squad have experienced a Welsh derby, with Sunday's game at the Liberty Stadium the first meeting between the clubs in five years.
But Warnock felt his squad would be able to cope as they look for their first Championship win on the road.
"I think we have people with the character you need in derbies. I look at Marlon Pack, Sean Morrison. I think you need the characters to stand up and be counted," Warnock said.
"But, for somebody who might not be one of the big names, there is always a hero in the derby. You talk about the goal five years ago, people remember things.
"They have all got an opportunity to be remembered in years to come."
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All pictures via Getty Images.