Watford players are not interested in the club's history with Everton boss Marco Silva.
The Portuguese returns to Vicarage Road after being sacked in January under controversial circumstances, with the Toffees blamed for tapping up Silva.
But Foster says the incident will not have an impact on tonight's game.
"I am sure it will have an impact from the club's point of view in general," Foster said. "But it is not something me personally or any of the players out on the pitch on Monday night will be thinking too much about.
"We will just be focusing on the job as usual, go about the game as we normally do and try to get the three points and hopefully we can put on a good display."