The former Barcelona No.1 signed for the Red Devils in January 2015 and made two appearances at the end of last season in the absence of David De Gea.
But the Spain international was transfer listed last summer after allegedly refusing to represent United’s U21 squad and following several months of being made to train in exile at Carrington, is now on loan with Standard Liege until his Old Trafford contract expires at the end of the season.
It was recently revealed that incoming Manchester City gaffer Pep Guardiola has held talks with the 34-year-old, who he managed during four years at the Nou Camp, regarding a shock Bosman move to the Etihad Stadium.
But according to The Daily Star, who cite reports from Portuguese publication Record, Valdes could snub the noisy neighbours in favour of joining Sporting Lisbon.
The Primeira Liga outfit reportedly tried to sign the shot-stopper last summer and can offer him a greater chance of first-team football, with Joe Hart unlikely to be usurped from between City’s sticks any time soon.