Watford are tracking AC Milan defender Mateo Musacchio.
FCInterNews says Watford intend to post scouts to the derby on October 21 between Milan and Inter Milan.
Musacchio will be in their sights, as will Inter defender Andrea Ranocchia.
Ranocchia has previous Premier League experience, having spent the second half of the 2016-17 season on loan at Hull City.
Watford boss Javi Gracia is anxious about his defence and is seeking a new centre-half signing for the January market.