Controversy over the manner of Paul McGrath's move from Manchester United to Aston Villa for a fee of just £450,000 in 1989 is revived by the official launch in Manchester yesterday of Alex Ferguson's autobiography Managing My Life.

Ferguson's decision to allow the Irishman leave the club for a sum which, even by pre-90s standards, was ridiculously small, is regarded as one of the rare questionable judgments, the astute Scot has made in the transfer market.

On his own admission, he couldn't persuade McGrath to temper his drinking habits. This, and the need to break up the gifted but occasionally wayward triumvirate of McGrath, Bryan Robson and Norman Whiteside, Ferguson admits, was the reason for unloading the two Irish players.

McGrath, of course, went on to achieve outstanding success with Aston Villa and the Republic of Ireland in his post-Manchester career but according to Ferguson, it couldn't have happened if he'd stayed at Old Trafford.

"Graham Taylor, his new manager at Aston Villa, deserves credit for helping McGrath to pull himself together so successfully, that he shone over a number of seasons, not only for Villa but for Jack Charlton's Republic of Ireland team," writes Ferguson.

"Apparently, Graham gave him a minder to reduce the risk of backsliding and cossetted his ravaged legs by confining his training exertions to gymnasium work. Such easing of the load would have been hard to sustain at United where every match has the intensity of a cup tie and players must be rigorously trained to meet extreme physical demands.

"The improvement in McGrath's performance record after he went to the Midlands must, however, have had less to do with his limbs than with his head. He was reluctant to leave United and the jolt of having to move, may have prompted some private owning up about the dangers of his downward spiral."

"I'm convinced the changed McGrath we saw at Villa, would not have materialised at Old Trafford where he hid in a cocoon of unreality, surrounding himself with people who encouraged him to retreat to his drinking hideaways. It was presumably his attachment to that make-believe world, that was the main reason for him wanting to stay at United but I knew that he and we, would suffer if he did.

"I always sensed a fragility about the man and it was easy to feel sorry for him as a victim of his own nature. I did not for a moment, begrudge him the success he enjoyed after he left me."

Ferguson, the supreme disciplinarian, cites a long drinking booze by McGrath and Whiteside in the week leading up to an FA Cup tie against QPR in January 1989, as the reason why his patience with the players finally ran out, and he decided to sell both.

Unlike McGrath, however, whom he says, he could never reach, he had a vague rapport with Whiteside. "He was intelligent and would hold his hand up when called to account over his drinking. My rebukes did little good but at least in our talks, I felt I was communicating with Norman. That was never true of Paul McGrath."

Whiteside would later ascribe his shortage of pace to a bungled physiotherapy course, at the age of 15, which left him with permanent trouble in his hips and other joints. And according to Ferguson, it prevented him becoming a truly world class player.

"As a player he was close to the genius category. When I heard he had been a sprint champion at school, I began to picture the player that real quickness would have made him. It was natural to wonder if the pain of thinking what might have been, had something to do with the contempt for his career, that was implied by his consumption of booze."

Having finally emerged from the shadow of Matt Busby to take his place among the outstanding managers of our times, Ferguson can now reflect with some amusement on the days when his career at Old Trafford hung by a thread, back in the infant days of the decade.

Victory over Crystal Palace in a replayed FA Cup final at Wembley in May 1990 changed everything, however, and set up a train of success which is still trundling on in the closing months of the '90s.

Also surviving, it seems, is some of the rancour which followed his dropping of goalkeeper, Jim Leighton, a fellow Scot, for the replay of that final. That judgement still rankles with a section of the faithful north of the border. And yet, it stands as impressive testimony to the affable Scot who never betrayed his professionalism by eschewing the difficult decision.

Managing My Life by Alex Ferguson (with Hugh McIlvanney). Hodder and Stoughton Price (£18.95 stg).