Sir Alex Ferguson revealed his 'biggest regret' as Man Utd manager that still annoys him to this day

Sir Alex Ferguson didn't even have to think when asked to name the biggest regret of his Manchester United career, and he admitted it still bothers him.

After 26 seasons in charge at Old Trafford, Ferguson left Manchester United in May 2013 having won an incredible total of 38 trophies with the club.

Over a decade after his retirement, the Scot is still widely regarded as one of the greatest football managers of all time, with some suggesting he is the best that the Premier League has ever seen.

During his time at the club, Ferguson is widely credited for making the best call for the team, regardless of who it may have upset or frustrated in the process.

But when he looks back at his career, there is one moment that stands out as a decision he massively regrets.

Sir Alex Ferguson is the most decorated British manager of all time. (Image: Getty)

With 13 Premier League titles and two European Cups to his name, Ferguson is the most decorated British manager ever.

But before the legendary manager led United to their second Champions League final victory, the United boss made what he now views as the biggest regret of his career, leaving Park Ji-Sung out of the squad.

“To win the European Cup is fantastic," Ferguson told MUTV.

“It was a really great bunch of players with a great attitude about them and a good, strong squad.

“My problem in the 2008 final, maybe I even regret it to this day, was I left Park Ji-Sung out completely in the final.

“He’d played such a great role and that’s the problem when you get to these finals. No player deserves to be left out of the final.”

Park Ji-sung and Sir Alex Ferguson had a close relationship at Manchester United. (Image: Getty)

Despite being viewed mostly as a squad player throughout his seven-year spell at Old Trafford, Park was clearly one of Ferguson's favourite and most trusted player as he was called upon during several of the club's biggest matches.

In their 2008 Champions League semi-final against Barcelona, the South Korean international played a key role and yet didn't make the cut for the final against Premier League rivals Chelsea, which United won the match 6-5 on penalties after a 1-1 draw in normal time.

Although he didn't allow it impact his strong relationship with Ferguson, Park admitted that missing out on the final was a big low point in his career and something that took him a while to come to terms with.

"I couldn't believe it," he later told UTD Podcast.

"I realised, when I got to the stadium, into the dressing room, I saw that there wasn't my shirt. Then I just go 'oh, I'm not in the squad today'. I don't know how I can say it, I was very, very disappointed.

"All my family was there, my whole country was looking for that because I played the semi-final. They were expecting that I would play the final, even probably on the bench. But I wasn't in the squad."