Marc Navarro made five appearances for Watford last season, which included only one start in the league.
Leganes tried to sign the right-back in January and AS reported in June they are still interested in the defender.
It was explained the Spanish side were looking for a ‘low cost’ move or even to sign the 24-year-old on a free transfer.
Over the weekend, AS claimed the player has ‘already made it clear’ to Javi Gracia’s side that he wants to leave Vicarage Road this summer as he wants to play regular football elsewhere.
Mauricio Pellegrino’s side are advancing negotiations with all parties involved to close the deal for Navarro.
The fullback has been interested in joining the La Liga club for months and Watford have finally given a ‘green light’ for him to sign for Leganes on loan.
It’s made clear that in no case the Premier League side will consider his sale, but Leganes intend to include an option to make the deal permanent.
Leganes are without a right-back in the squad and their priority is to strengthen that position. Their idea is to not spend heavily, which is why a loan move for Navarro fits their needs.