The Portuguese champions are looking into the signature of the Mexican international.
The club currently has two many foreign players and they have taken Daniel Pudil and Fernando Forestieri out of the club, sending them both to Sheffield Wednesday with Matej Vydra also set to depart.
Now it is being reported in Portugal that they may have another one departing, although this is one they want to keep.
Watford will not want to sell the player, he has become a regular in the first-team. However the club may decide to cash in and get rid of another foreigner from the first-team.
Layun is known to be enjoying his time in England but Porto want him on loan and then to buy him at the end of the season. The club also have until September 22nd to sign him from Watford, as the Portuguese window is open for longer than England's.
That would give the Mexican international a shot at Champions League football this season, something he would not have thought of when he left for the Championship last term.