The Italian looked to counter Leeds' three-at-the-back set-up by going with a three-man attack and, after weathering an early storm when United hit the post, they were able to cut loose as the game went on, especially as Leeds' numbers dropped.
Jason Pearce was shown a straight red card for a foul on Almen Abdi with the Hornets 1-0 up thanks to Matej Vydra.
Vydra struck again and his double were added to by Almen Abdi, Mark Yeates, Sean Murray and Troy Deeney
"We took a gamble in the first half, we made changes and we knew we would risk something at the back," he said.
"On the counter attack we looked dangerous and we could have even scored another goal. I tried to put a team on the pitch with good balance going forward, but I knew that playing in a game like today when Leeds wanted to win, we would have to leave spaces behind.
"The nature of the team I picked meant we would risk something. It was a very good result, I am pleased for our strikers because we needed a confidence booster and this will provide it," he said.
"To be honest, the fact that they had nine gave us a big advantage, but we did very well and used the extra man wisely. It proved to be a very good day for us."
The one down side for the diminutive Italian as he headed back down the M1 was a possible dislocated shoulder for Abdi.