The 26-year-old midfielder has been the subject of intense speculation over the past few months, with constant rumours linking the Portuguese international with a move away from Old Trafford.
Nani has fallen down the first-team pecking order and has become disillusioned with life at Manchester United, and Sir Alex Ferguson has admitted for the first time he is fighting a losing battle trying to convince the former Sporting Lisbon star to sign a new deal.
"[Chief executive] David [Gill] has been speaking to [Nani's] agent for quite a few weeks now," explained the Red Devils boss. "It's up to the boy himself.
"He's got a year and a half left, I would prefer to keep him to the end of his contract. But I think he wants guaranteed first-team football. But we can guarantee that.
"His performance the other night can guarantee that. We're trying our best because he's such a match-winning player."
Nani's substitute performance in last weekend's FA Cup fifth round victory over Reading showed why Ferguson rates the winger as "one of the best match-winners in the whole of Europe".
But, despite his impressive display, the player's pessimism has been unaltered, particularly with the imminent arrival of January signing Wilfried Zaha in the summer.
Gunners boss Arsene Wenger is a known admirer of Nani, and tried to bring the Manchester United star to the Emirates Stadium in the mid-season window. However, the north London club were put off by the £16million valuation slapped on his head.
Arsenal are expected to have money at their disposal this summer, though, and might look to push through a transfer.