This is reported by Sport.es.
According to the source, we are talking about renting until the end of this season with the option of a mandatory purchase.
Femenia is expected to fly to Russia to complete the deal next weekend.
Watford were eliminated from the English Premier League at the end of last season.
The 29-year-old Femenia played a total of 88 matches for the English club, in which he scored two goals and made three assists.
Earlier it was reported that the trial of "Spartak" in the case of violation of sanitary standards will take place on October 12.