are signing Le Havre midfielder Pape Gueye but are expected to send the 20-year-old on loan to Udinese.
The Hornets are looking to boost their ranks by bringing in highly rated young players from across the continent.
Gueye will return to Watford later down the line to fight for a place at Vicarage Road.
One man who could be set to leave the club is star name Abdoulaye Doucoure, who is wanted by London rivals Arsenal and Tottenham.
French giants Paris Saint Germain have also been mentioned in the same conversation as Doucoure, with the player yet to offer any assurances about his future.
Watford finished last season two points behind West Ham in eleventh place, and will look to break into the top 10 next season.