The Belgium international was the subject of a high-profile transfer in the summer of 2013, with former Everton boss David Moyes returning to Goodison Park to raid the ranks.
Fellaini struggled to justify his hefty £27million price tag, though, and came under ever-increasing pressure as his form dipped and Moyes was ushered towards the exits.
He is, however, a proven Premier League performer and was among the goals again at the World Cup finals as his trademark header helped Belgium to a 2-1 victory over Algeria.
Vertonghen was not surprised to see the 26-year-old shine on the grandest of stages, but has warned United that they need to start playing to his strengths if they are to get the best out of him at club level.
The Tottenham Hotspur defender said: “Marouane always is very important for the Belgian team.
“I know there has been a lot of pressure on him from the fans in England, but in Belgium he always does well and scores goals.
“I’m very pleased for him and I gave him a little hug after the game because I know that goal meant a lot to him.
“Marouane is a very cool guy. The pressure doesn’t really bother him too much.
“We know how to use him and I don’t know whether they do in his other team.”
Manchester City skipper Vincent Kompany, another of Fellaini’s international colleagues, is also of the opinion that United need to give the tough-tackling midfielder more time in which to show his true colours.
He said: “Fellaini is a terrific player and any player in his first season at a new club, it can be tough.
“You have to grant players a couple of seasons before you can judge someone. For us, with Belgium, he has been doing it time and time again.
“Players like Dries Mertens, as well, are our weapons coming off the bench.”