1 Andy Cole
Cole left Old Trafford for Blackburn in 2001, his nose put out of joint by Ruud van Nistelrooy's arrival at Manchester United. "I regret leaving," Cole has said since. "If I hadn't been so headstrong and stubborn I could have stayed. I wasn't playing regularly but leaving was the wrong decision. I'd just signed a new contract and had a fantastic relationship with the manager. I should have stayed."
2 Gabriel Heinze
The Argentina left-back left United after failing to force through a transfer to Liverpool when he became disgruntled by losing his place to Patrice Evra. Although he subsequently enjoyed success at both Real Madrid and Marseille, Heinze, now 35 and at Newell's Old Boys, has long rued his decision to force Sir Alex Ferguson into selling him. "I don't have many football regrets but I regret leaving Manchester United," he said. "I was impulsive and strong willed and it meant leaving a great club."
3 Henrik Larsson
The retired Sweden striker says his "only regret" in football is not accepting Sir Alex Ferguson's invitation to extend his three month loan at United from Helsingborgs in 2007. "If there is one regret I have about my career it is that I returned home to Sweden when Mr Ferguson was trying to get me to stay at Manchester United," Larsson said. "I should have stayed at United for longer."
4 David Beckham
After leaving Old Trafford in 2003 it took Beckham four seasons to win his one and only La Liga title at Real Madrid – and that came at the end of a season in which he had fallen out with and initially been overlooked by Real's coach, Fabio Capello. Wonderful as the experience of playing for Real, LA Galaxy, Milan and Paris Saint-Germain has been Beckham arguably never again hit the heights he achieved in Manchester.
5 Roy Keane
Keane departed United suddenly in November 2005 in the wake of growing tensions with Ferguson and his criticism of the club's young players. He went on to join Celtic but, less than a year later, had retired. "The day I left United I should have stopped playing," Keane has said. "I lost the love of the game that Friday morning [when he departed]. I left Old Trafford and I thought 'football is cruel, life is cruel'. I look back and I think I should have said this and I should have said that."
6 Jaap Stam
The Holland defender was sold to Lazio for £16.5m in 2001 after his autobiography annoyed Ferguson. The manager later conceded it had been an error and although Stam starred for Lazio, Milan and Ajax before retiring in 2007 the former centre-half regards his time at United as the zenith of his career. "I don't hold grudges," Stam said. "But United know they made a mistake selling me. I haven't done too badly since I left but Old Trafford will always hold the happiest memories for me."
7 Dimitar Berbatov
Berba's unhurried elegance, acute football intelligence and wonderfully understated economy of effort were shown off on the perfect stage at Old Trafford. He may have played more games since joining Fulham from United last summer but much as we all enjoyed his "keep calm and pass me the ball" T-shirt the Bulgarian striker cannot have relished life on the fringes of a relegation battle and is now being linked with a move to Galatasaray.
8 Nicky Butt
Eulogised by Pelé as England's best player of the 2002 World Cup, Butt left Old Trafford two years later to join Newcastle and the central midfielder arguably never looked anywhere near as good again. Stints with Birmingham (on loan) and Hong Kong's South China followed but Butt was delighted to return to United as a reserve-team coach last November.
9 Dwight Yorke
The only way was down for the striker after Yorke left Old Trafford in 2002 for Blackburn where he soon fell out with the manager, Graeme Souness. Moves to Birmingham, Sydney FC and Sunderland followed.
10 Kieran Richardson
Hopes were once high for the left-winger but Richardson's career has been on an inexorably downward trajectory since he swapped United for Sunderland in 2007. Now struggling to get a game for Fulham.