Former Manchester United assistant coach Rene Meulensteen admitted the club were powerless to stop Gerard Pique rejoining Barcelona in 2008.
Letting Pique leave United backfired for Sir Alex Ferguson as the Spanish international went on to become one of the world's great centre-backs, winning eight La Liga titles and three Champions Leagues at his boyhood club.
But Meulensteen, Ferguson's assistant from 2007 to 2013 — and United's reserves and youth manager before that — said the arrival of Nemanja Vidic made opportunities hard to come by for Pique. He added that there were also concerns among the United coaches about whether Pique would suit the Premier League.
Pique left United for £5million having made just six league starts.
The Dutch coach was also asked by The Michael Anthony Show podcast about Jonny Evans, with United having struggled to replace Vidic and Rio Ferdinand at centre-back.
On Pique's departure and the regrets United could have, Meulensteen said: "I know, I understand that, but you also had Ferdinand, Vidic, Wes Brown and John O'Shea, that's how the club looked.
"The reason why Pique was gone was that Gerard was a very strong minded person. He knew exactly what he wanted and he knew he was good enough to play first team football. However, was Gerard the ideal and right centre-back for a league like the Premier League?
"It has to be said 'not too sure'. I'm sure he would have become okay because I'm a big fan of Gerard but the proof is in the pudding for him — he made the right decision. He's one of the most decorated players.
"The problem we had is Vidic just walked through the door half a year before."
It was widely reported at the time that Barcelona could exercise a clause in Pique's contract to bring him home and Meulensteen confirmed that was one of the main reasons for his return to Catalonia.
"I think there was some sort of agreement in a clause with Barcelona and Manchester United and I'm 100 per cent sure that Gerard pushed for that guarantee," he added.
"They [Pique and Evans] were both good at carrying the ball out from the back, moving the ball forward. That's one of the reason why they were fantastic."
