Everyone can agree that the great Sir Alex Ferguson took charge of some breathtaking talents during his 26-year reign as Manchester United manager.
The Scotsman was blessed with several superstars at Old Trafford, from Paul Scholes and Ryan Giggs to Eric Cantona and five-time Ballon d'Or winner Cristiano Ronaldo.
Man United won an incredible 38 trophies under Ferguson, including 13 Premier League titles, and his ability to both identify and nurture talent is second to none.
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The aforementioned Ronaldo regards Sir Alex as his "football father", and despite dishing out the hairdryer treatment multiple times, he was renowned for his man-management skills.
However, there is one Champions League and European Championship winner that he couldn't convince to join Man Utd - and he's still annoyed about it today.
The player Sir Alex is mad at for not joining Man Utd
The player in question is Oliver Kahn, who became one of the greatest goalkeepers the game has ever seen during his legendary career at both club and international level.
Kahn enjoyed unbelievable success with Bayern Munich between 1994 and 2008, winning 22 trophies in total and breaking all sorts of Bundesliga records.
The 2002 FIFA World Cup Golden Ball winner enjoyed his time in Bavaria, however he now regrets passing up on the chance to join Ferguson and United when it was presented to him.
“Sir Alex Ferguson is still mad at me today," 48-year-old Kahn told Bild, via Goal. "He thought that I would move to Man Utd in 2003 or 2004.
"But I was more interested in trying to define an era at Bayern. Looking back, I should have done it then (joined Man Utd). It would have been a nice challenge for me.”
Having played 557 Bundesliga matches, no 'keeper has made more appearances in the German top-flight than Kahn, but Fergie would have loved him at United.
At his best, he was commanding, aggressive, and who knows what would have happened had he and Sir Alex spent a few years in each other's company.
Kahn on 1999 CL final
In the same interview, Kahn also reminisced about United's dramatic comeback over his Bayern side in the 1999 Champions League final.
The 48-year-old was in goal at the Nou Camp, and he joked: "I remember the Champions League final against Manchester United as a win – I just forgot the last two minutes."
Do YOU think Kahn would have had an equally successful career at Man Utd? Have YOUR say in the comments box below!