Andre Gray, Nathaniel Chalobah and Domingos Quina were left out of Watford's squad to face Southampton "to ensure the health and safety of all players, staff and officials", following an alleged lockdown party.
The trio's omission comes after the club launched an investigation into claims alleging that two of their players broke government lockdown rules by attending a gathering at Andre Gray's house on Friday night.
It is claimed in social media posts that team-mate Quina was among those who attended the house party, which was held on the striker's birthday.
In a story published by The Athletic, Watford officials are described as being "disappointed" by the breach, which was revealed to have taken place in a series of now-deleted videos on Gray's Instagram.
A statement on the club's website said: "Andre Gray, Nathaniel Chalobah and Domingos Quina have all been omitted from the Watford squad by Nigel Pearson to ensure the health and safety of all players, staff and officials at today's game."