A former Dundee United and Rangers footballer was sentenced to three months' imprisonment yesterday and could face civil action after ''savagely attacking'' an American doorman ''in one of the worst assaults'' ever seen by a bouncer with 12 years experience.

Sandy Robertson, of Cedar Grove, Dundee, was found guilty after a trial of punching, stamping and kicking an American doorman outside an Edinburgh restaurant/pub complex while celebrating his 26th birthday.

Robertson has now received a letter from the lawyers of victim John Richardson threatening to sue for the injuries suffered.

Defence agent Robert Fairbairn said the footballer was currently being ''scouted by professional teams'' after parting with Dundee United on amicable terms.

He explained that the accused, who was signed by Rangers at 16, left school without qualifications and knew no other career.

Edinburgh Sheriff Court heard during the trial that Rob-ertson, who already had a previous conviction for a in 1991 - turned nasty when he was barred from the Dome complex in Edinburgh's George Street where he had been drinking with friends on Friday, April 25.

Mr Richardson - who had been in Scotland for almost six months training with a football team in Livingston - said that, after leaving the complex, Rob-ertson became a nuisance, trying to get back inside and blocking the revolving door.

''He was obviously inebriated. I could tell from his red face. His eyes were half shut, he was almost swaying and speaking very slowly.''

Initially Robertson, who was joined by friend Brian Klimioenek, of Ferniehill Drive, Edinburgh, had been good natured.

''He kept shaking my hand saying big man's my friend. He was a nice enough fella. It wasn't a problem at all. I just put my arm around his shoulders and walked him away,'' Mr Richardson said.

But then Robertson turned aggressive ''in a huge mood swing'' and grabbed hold of the doorman's lapels.

The six foot three inch, 16- stone bouncer was forced to push Robertson and his friend down several stone steps.

But as Mr Richardson, 24, stepped back up the stairs to retrieve a watch, he was assaulted from behind.

''That was the last thing I could remember until I saw a police officer in the front office of the Dome,'' he told the court. ''My lip was swollen several times the size it should have been. It felt like my whole head was swelling and both my eyes were swelling.''

The American, who returned to the United States soon after the attack, was taken to the Edinburgh Royal Infirmary but found to have no fractures.

Another bouncer Stephen Budding, 33, who witnessed the incident, said the victim had ''dropped like a stone'' when he was punched in the head and then kicked in the groin by Robertson.

''The doorman had turned away and one of the guys ran up behind him and punched him on the back of the head,'' Mr Budding said. ''That stunned him and as he crumbled he was kicked in the groin and dropped like a stone. The guy then stood on his head and stamped on it three times, hard and fast.

''It looked fairly savage. I've been doing this job for 12 years and its one of the worst assaults I've ever seen. I wouldn't want my head between concrete and somebody's boot like that.

''The doorman was left in a mess. His mouth had been burst open and blood was pouring from it. He was curled up on the ground, unconscious.''

Robertson admitted to procurator-fiscal depute Neil Allan that he had argued with Mr Richardson when the doorman refused to let him return into the Dome to find a friend, but denied attacking the American.

He said he had become angry when the doorman threw him down several stone steps, but claimed he had merely walked away.

When asked by Mr Allan how the bouncer wound up on the ground unconscious, he said ''I don't know'' and accused witnesses, who had identified him as the attacker, of lying.

Mr Fairbairn told the court that Robertson ''was not the type of young footballer often read about in the papers, attached to large clubs who have too much money and not enough commitment to training and just go out and cause mayhem in airplanes and the like.''

He said the accused was always willing to help young players and regularly made presentations at boys' clubs.

Sheriff Brian Hughes, who said he had ''no hesitation in finding the accused guilty'', sentenced him to three months jail.