The Hornets edged a tight first half but were back to their best after the break, playing some excellent football and cutting through relegation-threatened Blackburn through two-goal Troy Deeney and further strikes from Almen Abdi and Matthew Briggs in a 4-0 win.
Rovers also had Leon Best sent off in injury time after a coming together with Marco Cassetti.
"I thought we did well first half. The first goal was always going to be crucial after the backlog of games," he said.
"I'm disappointed in the manner we conceded but you've got to give credit to the lad who took his goals well. We were disappointed with how we reacted, we've not been like that.
"It was probably a big game too many for us but we've got to regroup quickly, we've remained positive and calm throughout and that's exactly the message we've said to them again.
"We've always known we had a game in hand, we always said it might come to goal difference, we've just got to go game by game again but at 0-0 I couldn't see that coming in the second half."
Blackburn last week