The Former Villarreal player signed for Manchester United in 2016 but he has struggled to hold down a regular starting berth under Ole Gunnar Solskjaer.
Bailly needs to move on in search of regular first-team football and a return to Spain could be ideal for him.
The Manchester United defender has a contract with the Premier League club until the summer of 2022 and he has been linked with the likes of Arsenal and Tottenham as well.
Meanwhile, Pau Torres is rated highly in Spain and he has a big future ahead of him. It would be quite a coup for Manchester United if they manage to secure his services at the end of this season.
The Premier League side will have to pay over 60 million pounds in order to sign the Villarreal defender.
The likes of Harry Maguire have been quite inconsistent this season and bringing in another quality centre back would be the right decision for Manchester United.
Increased competition could help the players at the club improve their game and in turn improve the squad.
A move to Manchester United would be a step up for Pau Torres and he is likely to be tempted if the Red Devils come forward with a concrete offer in the summer.