Fernandes is reportedly close to signing a £50m (€58.6m) deal to join the Red Devils but Mendes said Old Trafford is not the 25-year-old playmaker's only option.

After scoring eight goals in 16 Primeira Liga appearances this season, Portugal international Fernandes is in demand across Europe and Mendes, who does not directly represent the player, heaped pressure on United with his comments to Sky Sports.

"If he doesn't leave now, he will leave for sure in the summer because Sporting have already spoken with other clubs," said Mendes.

Fernandes played in Sporting's 2-1 Taca da Liga defeat to Sporting Braga on Tuesday and his most recent goals for the club came when he scored a brace in a 3-1 Primeira Liga victory at Vitoria Setubal earlier in January.

United boss Ole Gunnar Solskjaer has struggled to find adequate cover for injured midfielder Paul Pogba this season and the capture of Fernandes would strengthen the Premier League club's hopes of a finish inside the top five.

Mendes said that a deal will not necessarily be completed before the end of the January transfer window, saying: "Something will happen but I am not sure if now or at the end of the season."