The Hornets' 1-0 victory at the Riverside saw them move up to 10th place in the Premier League standings, with 11 points from eight games played.
After a poor start to the campaign, the Hertfordshire outfit have now won three and drawn one of their past five games.
They have conceded 13 goals so far this term, eight from balls crossed into the box, but managed to blank Boro on Sunday after some half-time adjustments, as the Italian explained.
"We put a lot of attention defensively, what I mean is crosses, corners and free-kicks, which we were allowing a lot more in the previous games," he said.
"In the first half we were making some mistakes on the right side, we were allowing them too much space. I corrected some of the things at half-time and we didn't allow them anything else for the second half."
Punters looking to use a free bet might fancy Watford to push on and finish in the top 10 and they are next in action against Swansea on Saturday, October 22.
And the former Napoli tactician certainly feels there is more to come from his side as they look to establish themselves as a top-flight club.
"On the performance it was very good defensively, but I think we can do better in the overall of the game," he added. "We have done much better in the other games before this, except for Burnley."