Manchester United winger Nani admitted his future at the club was uncertain as speculation continues to mount he could be heading for the exit door at Old Trafford.The 26-year-old endured an inconsistent season as United reclaimed the Premier League title, falling down the pecking order as new boy Robin van Persie grabbed the limelight.And with only a year left on his contract, rumours are circling the club have slapped a £8.5 million price tag on the Portuguese international.But Nani said he is remaining calm despite the unclear nature surrounding his career."My future? Nothing is certain," Nani told reporters. "I am calm. I have everything in my hands."I am not saying that I will not continue at Manchester United. I will think about what is best for me."However, Nani is confident he will not be returning to his native Portugal, believing he is playing at a different level than the Primeira Liga."I have respect for the Portuguese clubs, especially Sporting Lisbon but also Benfica and Porto, but I don't think that is viable," he said."I think my level at the moment is different."