The youngster made his debut under Louis van Gaal last season against Arsenal and went onto prove himself against many different Premier League clubs.
His most memorable moment was against Tottenham Hotspur, moments after he was substituted off for Matteo Darmian, Spurs found the back of the three times in eight minutes.
Speaking about his talent, Parker insists Fosu-Mensah has plenty to offer Mourinho’s side.
“The position United have to worry about is right-back. They have Fosu-Mensah who is absolutely perfect,” he said.
“He is a very good defender and in the final third he’s as cool as a cucumber. He never panicked last season and has an arrogance on the ball. He would be a better bet than Valencia who is fine up to a point but doesn’t have a trick.
“The thing that goes against Fosu-Mensah is that he’s young and Mourinho doesn’t like young players. It’s the same old story and if that’s what is keeping him out of the side that’s a concern.”
Fosu-Mensah has looked spectacular each time he has played on the first-team, however Valencia looks like a new player under Mourinho this season.
He has been racking up assists from right-back and has vastly improved on his game from under Louis van Gaal last campaign.
The Dutchman will be hoping to get ahead of Valencia at some point this season, but it will be hard for Mourinho to displace Valencia when he’s in such fine form so it looks like we’ll be seeing him in action for a while.