The Boro head coach has always been advocate of a 4-2-3-1 formation which he has used throughout his near three years on Teesside, and it has served him well in helping get the club back into the Premier League last season.
However, the system does not appear to be working as well in the top flight, with Boro suffering their fourth defeat in five games against the Hornets and still looking for a first win at the Riverside Stadium this season.
Boro only had one effort on target at the weekend - a tame strike from Adam Forshaw - and have only scored four goals in the last six games.
A daunting trip to Arsenal is up next for Boro on Saturday, with Karanka adamant that he will stick with his tried and trusted formation regardless of growing numbers of supporters calling for him to start playing Jordan Rhodes up front alongside an isolated Alvaro Negredo.
The Spanish tactician said: "I have to think about every single game.
"We got promotion with one up front, and I don’t think we need to change now. We have our style, and I built a squad to play that way.
"Every single defeat is difficult, especially at home, and especially when we are a strong team at home. But we have to keep going. We have a strong group, and it is October so there is a long way to go.
"We have to recover physically and mentally. I know for everyone, it is not a nice moment. But we have to be positive because if we do not believe in ourselves, who can believe in us?"