The Portugal international is convinced the team can get back on track again and regain their confidence, but he warns they can only do that by making their own ground a fortress.
West Brom and Southampton have already taken points off the Red Devils in their own backyard this season, with the Baggies causing the biggest upset of the lot with a surprise win over them at the so-called 'Theatre of Dreams'.
However, Nani is certain their 1-0 victory over early Premier League pacesetters Arsenal in their last game at home could be the turning point for the squad following a transition phase in the wake of David Moyes' arrival in the summer as Sir Alex Ferguson's successor.
He said: "It looks like teams are more confident when they come here to play against us.
"But I'm sure we will change that because, at the moment, we are playing without all our confidence. I think once results start coming we will show who the real Manchester United are and will do much better."
Nani's views were echoed by coach Phil Neville, who sensed a sea change in the players in that performance against the Gunners, which demonstrated that a bond is beginning to be formed between the group and their new manager.
The former United player, who returned to Old Trafford from Everton following Moyes' appointment, said: "The players are beginning to trust the manager and his philosophy and I think you saw that against Arsenal.
"It was always going to take a bit of time after one man had controlled the club for so long, there was always going to be a transition period."