Sir Alex Ferguson spent close to 27 years as Man United boss before bowing out in 2013 after winning the club's 20th Premier League title.
During his tenure, United established themselves as a formidable side in England and the Scottish is widely credited for Man United's overall success.
However, despite his otherwise glittering career as manager, Ferguson also had his shortcomings at Old Trafford, including signing flops such as Eric Djemba-Djemba and Bebe who never lived up to their billing.
And in his own admission, Ferson believes there are things he could have done differently if he had a second chance.
In an exclusive interview with MUTV, Ferguson revealed agonising over a selection decision for the 2008 Champions League final against rivals Chelsea remains his greatest regret.
At the time, teams were only allowed to list seven substitutes in Europe's elite club competition, compared to the 12 permitted on the bench for the most recent final between Liverpool and Tottenham.
The guideline presented the 77-year-old a dilemma on who should make his his squad for the day.
Former South Korea international Ji-sung Park eventually emerged among the unlucky players who missed out on a spot, a difficult decision Ferguson had to make in his time in football.
"To win the European Cup is fantastic. It was a really great bunch of players with a great attitude about them and a good, strong squad," he said.
"My problem in the 2008 final, maybe I even regret it to this day, was I left Ji-sung Park out completely in the final. He'd played such a great role and that's the problem when you get to these finals," Fergie conceded.
The legendary manager further recalls a similar fate befell Dimitar Berbatov in 2011 during the Champions League against Barcelona.
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