Former Norwich City stars have paid their own tributes to legendary Manchester United manager Sir Alex Ferguson following the news that he will retire at the end of the season.

After nearly 27 years in charge at Old Trafford, Ferguson's last game will be the Premier League trip to West Bromwich Albion on May 19 and he will join United's football board.

Ex-City goalkeeper and manager Bryan Gunn, who has known Sir Alex professionally and personally since he signed him on schoolboy terms at Aberdeen, described him simply as 'a great man'.

Hull manager Steve Bruce, who was Norwich skipper when Ferguson took him to United in 1987 and went on to captain the Double-winning team of 1993-94, said his former boss was an 'impossible' act to follow.

And Huddersfield boss Mark Robins, who joined the Canaries from United in 1992, said Sir Alex was the best manager ever.

Ferguson's career haul of 49 trophies as a manager includes two Champions League wins, the European Cup Winners' Cup, 13 Premier League titles, five FA Cup wins, and four League Cup successes with United. Before that, he won the Cup Winners' Cup, three Scottish Premier League titles and the Scottish Cup four times with Aberdeen.

Gunn was with his 71-year-old former boss just 48 hours before the announcement of his retirement, and was taken aback by the news.

He said: 'I was with Sir Alex on Monday at a Rangers v Manchester United legends game at Ibrox.

'We talked about his golf day at the Belfry in July and his forthcoming hip operation but there was no inkling that he was about to announce his retirement.

'Now the next 10 days up to his last game will be filled with people's memories of the great man.'

Ferguson has been a significant figure in Gunn's life in good times and bad – he signed him for Aberdeen, sold him to Norwich in 1986, attended his wedding in 1989 and his daughter Francesca's funeral in 1992, and brought a United team to Carrow Road for his testimonial in 1996.

'I first met him when I was 14, when Eric Black and I went to Aberdeen for a week's trial,' said Gunn. 'At the end of the week, he called us in for a chat and said he'd like us to sign for Aberdeen on schoolboy terms.

'He was a young manager then. He had been successful at St Mirren and was then beginning to make the kind of shrewd signings that built Aberdeen into the team they would become, challenging the monolopy of Rangers and Celtic and winning domestic trophies and then the European Cup Winners' Cup. It was an incredible time as a player growing up, and a time that club will probably never repeat.'

Gunn also became the Fergusons' babysitter – looking after another future manager in son Darren.

'Sir Alex has three sons and the youngest were the twins, Jason and Darren. Alex would pick me up in his silver Mercedes. His wife, Cathy, would ensure there was a sandwich waiting for me and it was my way of spending Saturday nights, watching TV or playing in his snooker room,' he said.

'He took an interest in his squad and passed on his knowledge and it's amazing how many players at Aberdeen and United have gone into management.

'It was apparent by then that big clubs were looking at Sir Alex and once Manchester United showed an interest, it was the only club in his sights.

'He had a difficult start but with his persistence, his courage and his knowledge of football, he restored United to the force they had been.'

Ferguson's second game in charge of United – and his first point – was a goalless draw at Norwich in November 1986 and City had some impressive results against Ferguson's team under Ken Brown and Dave Stringer.

'We had a good record but they got the upper hand with that first Premier League title in 1992-93,' said Gunn.

'His attitude was there was always room for at least one trophy in the cabinet every year. He had an ambition to win everything he went into and if I was picking a quiz team he'd be the first person in it because his knowledge of everything, not just football, is second to none. He is a great man.

'He played a big part in my career and I'm just delighted to have been involved in a small part of his.'

Bruce said Ferguson's interest in his players extended beyond their playing careers – even when he opposed them as managers – and he had been in touch to congratulate him on Hull's promotion to the Premier League.

'He wants to beat you, for certain, and he does that constantly,' said Bruce. 'But he offers you a bit of encouragement and if you pick up the telephone, he'll always come back to you. And I think he has a humility about him, from his working-class background. He'll treat the groundsman just as well as he would treat his star centre-forward.

'He has a fantastic humility, for all he's achieved, and we wish him well.

'I spoke to him a couple of days ago and there was no hint of anything about retirement. It was just a simple text message and a short conversation wishing me good luck for the weekend and after that, a text to say well done.

'I think he'll do that for most managers, especially the young ones. He'll always give the encouragement that any young manager needs.'

Bruce told Sky Sports News that Ferguson's example had inspired many of his United generation into becoming managers.

'The big thing for all of us is that he takes you to Old Trafford to start with,' he said. 'That in itself for any player going there, it's arguably the biggest club in the world, with an unbelievable support. Anywhere you go, everybody wants to beat Manchester United. When you come away from it, it's the first thing you look at – when are we going to Old Trafford? Whoever has gone to play for him, it rubs off on you, this winning mentality he's got. People ask what's he like and he's so driven, so determined and works so hard at the job. It's the next step for all of us, when you finish and you hang up your boots. What are we all going to do? It's no surprise that a few of us have gone into management and coaching.

'He sets such high standards, he's very difficult to follow or copy. It's impossibly to try to copy somebody like him. He's just been remarkable.

'Whoever takes over, it's going to be some act to follow because you look back over 27 years and the trophies he's won and it doesn't seem quite right Fergie won't be in charge of Manchester United any more. It's quite remarkable and I don't think the next manager will do 27 years.'

Former striker Robins, who has often played down the theory that he saved Ferguson's job with his winning goal in the FA Cup third round against Nottingham Forest in 1990, said simply: 'He is the best football manager to have ever graced the job, without a shadow of a doubt.'