David Moyes revealed his was put off signing Harry Maguire at Manchester United in 2013 because of concerns over his size.
The former Red Devils boss revealed that Maguire was scouted by Old Trafford staff, but they passed up an opportunity to sign him from Sheffield United.
After spells at Hull and Leicester, Maguire became the world's most expensive ever defender last week when Manchester United splashed £80million on him.
And ex-United manager Moyes joked on talkSPORT that he was put off bringing Maguire to Old Trafford six years ago because of his "big a**e".
Harry Maguire was named man of the match on his Manchester United debut against Chelsea
David Moyes revealed Manchester United were concerned about Harry Maguire's size when they scouted him in 2013
Moyes said: "We didn't try to sign him [at Man United] but we flagged him up at that time.
"I was very aware of the players in the lower leagues and had a made good career out of bringing them to Everton - whether that be Tim Cahill or all the ones we did through the years.
"Harry Maguire was another one I recognised. He played against Preston North End at home in a league game and I watched him and thought he played really well but at that time he was really big - he had a big a**e. You thought 'my goodness, how big is Harry going to be' because he was a relatively young boy at that time.
"To be fair he looks in terrific shape and he hasn't changed at all really. When I went to United, we had Vidic, Rio, Jonny Evans, Michael Keane, Phil Jones, Chris Smalling.
"So for us to go and buy another young centre-half wasn't the biggest thing we needed at the time.
"And Harry Maguire has had to go on his journey. Sometimes the players need the journey to get to where they have to go. He might have struggled then."
Maguire was named man of the match on his debut as Manchester United crushed Chelsea 4-0 on Sunday at Old Trafford.
He said: "It's a great start for myself and the team.
"We rode our luck a bit in the first half. We gave them too many chances and were sloppy on the ball but in the second half we were much better.
"We only kept two clean sheets at home last season and we have really got to make it a hard place to come and score."