The creative midfielder has had very few chances to succeed since leaving the Lions in 2002 to take on a challenge at Newcastle United under Bobby Robson.
Although Valencia have not named their coach for the new campaign, Los Che have allegedly told the Portuguese that he is still surplus to requirements at Mestalla and that he will be sold if a good offer arrives.
And Sporting, aware of the player's situation, are lining up a move for the 25-year-old, which, if finalized, will result in his third stint at José Alvalade after one season on loan from Newcastle in 2004.
Viana, who is currently on loan at Osasuna, hopes that a return to Sporting will reignite his career, having failed to be called up for Euro 2008.
Goal.com - Portugal - Sporting Want Viana Return