Defeat during next Monday's Manchester derby will see United lose their grip on the top spot to rivals Manchester City.
Despite seeing an eight-point lead cut to just three, Nani is adamant that the Red Devils still have a good chance of sealing the club's 20th league title.
"It's a huge game [at City] and there will be a fantastic atmosphere there," he told MUTV.
"It will be a difficult game, but if you want to win the league you cannot think about the atmosphere or the opponents, we must just think about the way we play and try to win the game."
"Of course [we can still win the league]. We have to keep believing in our qualities because we still have a great opportunity to win the title."
Nani found the net during yesterday's 4-4 draw with Everton at Old Trafford.