Lille midfielder Cheikh Niasse is attracting Premier League interest.
The 19 year-old has broken into Christophe Galtier's first team plans this season and his emergence has sparked interest from across Europe.
Watford are keen, along with Rennes and Mainz, with the winter market about to open, says RMC.
LOSC management are eager not to lose Niasse, though will sell if the right offer arrives.
It's been suggested Watford are willing to take the midfielder on a six-month loan with the option to buy outright in June.