Having won everything he won, you'd think Sir Alex Ferguson would have very few regrets from his 27 years at Old Trafford, but one big regret he does have involves the South Korean winger Park Ji-Sung.
The now-retired former international was often deployed by Fergie when it came to big matches when he wanted to stifle the opposition's playmaker, and he famously did the job so effectively on numerous occasions.
One of Park's most famous performances came at the expense of Andrea Pirlo, in 2010. Image: PA
In fact, Park did his destroying act several times on route to the Red Devils' victorious Champions League run back in 2008, but didn't feature in the final against Chelsea.
That decision to leave him out still irks Ferguson every day.
Speaking in an interview with MUTV, via the Metro, Ferguson explains: "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.
"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.'
"At Wembley [in 2011] I did it to Dimitar Berbatov and he took it badly. He didn't deserve it. No player deserves to be left out of the final.
"That's why we try hard at these European seminars with the coaches to try to get 11 subs in the final. You've got four or five sitting in the stand who made fantastic contributions in getting there."
Berbatov and Park both missed out on Champions League finals despite enjoying impressive seasons for United ahead of the respective finals. Images: PA
Any Manchester United supporter will know too well the contribution that Park made during his time at the club, and Berbatov too for that matter.
But what do you make of Ferguson's comments about having 11 subs in European finals? Would you be all for it?
Let us know in the comments section, below.
Featured Image Credit: PA