Watkins bagged a hat-trick as Villa ran out 7-1 winners to cap a stunning weekend in the Premier League.
"We saw how high they play and the game plan was to try and get in behind them and you could see it worked," he said.
"We fancied ourselves today but I'm not sure we thought the scoreline would be that.
"It was more about blocking off the passing lanes and just making sure they can't pass through us. We knew it would be hard but we all worked together and it showed tonight."
Watkins opted to join Villa after Brentford failed to reach the top flight.
And he added: "Before the game I didn't think I'd score three goals but after the first one I got confidence and grew into the game and got chances.
"I should have got more in the end. One on one with the keeper... I've got to be scoring that. You can always improve and I think I'd back myself to score that."