"In English football it is difficult," he told Sky Sports.
"We wanted continuity after Manchester United but we didn't get it and tomorrow I will speak to the players.
"I am not happy with this performance, until now I have always said the performances have been good, that we were growing each game, but today this stopped.
"In every tackle they won, they went further to reach the ball. So Burnley were good, but we were not good."
Headed goals from Jeff Hendrick and Michael Keane condemned Watford to their third defeat of the Premier League season which saw them drop to 11th on the table, only above the Clarets on goal difference.