World Cup referee Hugh Dallas last night urged the Scottish players to ''think twice'' before making any rash challenges from behind in the opening game against Brazil.

Dallas talked after he had met members of the Scotland squad at their team hotel last night to go over new guidelines issued to whistlers on such tackles. The Motherwell-based referee, who leaves for France today, said he felt the Scots were well prepared and up to speed on the consequences of the new guidelines.

His comments came as Scotland manager Craig Brown voiced concerns that the opening game against Brazil would see the two teams being used as ''guinea pigs'' to test out the new FIFA recommendations.

''The referee and the players will have to be on their toes,'' said Brown. ''A careless tackle from behind which endangers an opponent is a red card, and the player will be off the pitch.''

He was happy with his team's disciplinary record in the games against Colombia, where they committed only 12 fouls, and the USA, where the count was even lower.

After having talked to Brown, Dallas said: ''I don't think that Scotland under Craig Brown have been guilty of such misdemeanours involving tackles from behind. I believe his players have been well prepared as to what referees have been told, and I'm sure Craig will keep that discipline going through the tournament.''

Dallas was not the only referee drafted into help the Scottish team last night, with rugby referee Jim Fleming also being brought to their East Kilbride hotel to talk to the players.

Fleming, who has refereed top rugby matches at the stadia in Paris and Bordeaux, where Scotland will play, told the squad of his personal experiences and went into such details as the length of walk to the pitch and whether teams would be standing together in the tunnel.

Brown's thinking is that players want to form an impression of every aspect in their own minds of what is ahead of them, down to the most intimate details. ''To be forewarned is to be forearmed in this tournament,'' said the Scotland coach.

Brown gave his squad a clean bill of health, but revealed that Celtic midfielder Craig Burley had to travel to London this week to receive treatment on a back injury, while Gordon Durie had responded well to treatment for a hamstring injury. Burley said the treatment given by a specialist in London, recommended by his former Chelsea team-mate Nigel Spackman, had cleared up the problem and he was back to full fitness.

In his parting message before setting off to France, Brown said he felt this had been the best prepared squad he had been involved with. He said their fitness and mental toughness was strong and they had the experience in their ranks, with players like Jim Leighton, Paul Lambert, and John Collins, who would not be intimidated by the big-match atmosphere. He admitted he had his starting line-up for the Brazil game in his head, and believed his players could cause an upset against them.

q Leighton states case - Page 47