Having the Spain international behind the Red Devils' defence has been a huge confidence boost for the 18-year-old, who claims his colleague is one of the greatest on the planet
Tim Fosu-Mensah hailed the performance of David de Gea against West Ham, describing the goalkeeper as "maybe the best in the world".
The 18-year-old defender impressed as Manchester United battled to a 2-1 victory at Upton Park on Wednesday to book their place in the FA Cup semi-finals.
De Gea made a string of fine stops as Louis van Gaal's men preserved their advantage, with Fosu-Mensah paying tribute to the Spain international as well as some of the team's senior players.
"David is one of the best goalkeepers in the world, maybe the best," he told the club's official website.
"It's very good to have a goalkeeper like that in your team. He can save you points or save you in the cup.
"I think players like Michael Carrick, Daley Blind and Chris Smalling kept the team together in order to win this match. It was very important because they give confidence to everyone on the pitch.
"I saw [Cheikhou] Kouyate score and thought 'no, no' but then I saw the linesman's flag so I was relieved it was offside.
"It was a very big game and a great win. I'm happy we won this game and that we can go to Wembley for the semi-finals. It's very special because it was a huge occasion."