Nani, 26, who is currently injured due to a hamstring injury, could be United's first player to be transferred after failing to sign a contract extension.
The Portuguese winger was once compared to former star Cristiano Ronaldo but after three years of regular football with the Red Devils, Nani has missed most of the season due to poor form or injuries.
To make matters worse, the winger was reportedly involved in a fight with talented United reserve player midfielder Davide Petrucci and was substituted during their UEFA Champions League match at Braga in November.
Meanwhile, United are reluctant on listening to Nani's £130,000-a-week wage demands with Zenit St Petersburg and Paris Saint-Germain ready to make a bid.
Nani is also facing heavy competition out on the wings with Antonio Valencia and Ashley Young preferred on either flanks while Wayne Rooney has been shifted to a deeper role in midfield.
With manager Sir Alex Ferguson plotting moves for Crystal Palace winger Wilfried Zaha and Porto's James Rodriguez, Nani's spell at Old Trafford could come to an end.