Watford boss Tom Cleverley spoke to BBC Three Counties Radio after his side was beaten 2-1 by Blackburn Rovers.
"For me, that was an unacceptable performance," he said.
"It was way, way short of the demands we put on the players and the standards we set for large parts of the season.
"It was completely below the level in all aspects of the game. For me, it has significance on how we can enter the summer and prepare for next season to ensure we don't fall short next season.
"We spent, I think, 10 weeks in the play-off places this season and next season we want to spend the last week in the play-offs, but performances like that are just unacceptable.