Nani believes Chelsea are the only side capable of challenging Manchester United for Premier League glory.
The title race appears wide open this season with just three points separating the top four teams heading into Christmas.
However, Portugal international Nani has written off the chances of Arsenal and Manchester City by claiming that only Carlo Ancelotti's Blues can stop United.
Chelsea's fine start to the campaign has unravelled and they have struggled for consistency in recent weeks, while City and the Gunners have also suffered some surprise defeats this term.
United remain unbeaten after 16 league games and Nani is confident they will go on to finish top if they stay ahead of the current champions.
"I no longer see anybody winning the Premier League this season outside of Manchester United or Chelsea. Hopefully, it will be United," he said.
Red Devils winger Nani has emerged as one of the most effective attacking players in English football over the past season-and-a-half.
He feels the departure of compatriot Cristiano Ronaldo in the summer of 2009 gave him the chance to flourish after a frustrating first couple of years at Old Trafford.
"It is easier for me to stand out now that Cristiano Ronaldo has left the club," admitted the 24-year-old.
"He is a fantastic player who got all the attention and deservedly so. I loved playing alongside him and we got on well together.
"But it is also true to say that, when he left United, it freed up space for other players to shine.
"When he left, I saw an opportunity to demonstrate my qualities and to show the people at United what I can do. That is exactly what I have done."
Nani has learned to combine his attacking instincts with better defensive discipline and he credits Sir Alex Ferguson for turning him into a more complete player.
He revealed: "Sir Alex Ferguson explained to me the importance of defending well and said I would end up being more dangerous in attack as a result. It is the truth."
Nani hopes to one day compete with the likes of Ronaldo for prestigious individual accolades.
He said: "I know I can become a better player and my aim now is to get on the list of nominees for next year's Ballon d'Or - the European Player of the Year prize.
"I want to leave my mark and hope after I retire that people will say Nani was a great player. I really want to do something special in my lifetime."
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