Watford boss Javi Gracia was left angry after their 3-1 defeat to Manchester City.
Gracia insists Sterling's first goal of three was clearly offside, as the Hornets lost 3-1 at Manchester City.
He said: "That decision, I think everybody could see what happened. This season, I didn't criticise the referees and I'm not going to do it today. If the officials want to explain what happened, they can do it. In my opinion it's clear.
"Today, in my opinion it's clear. Sterling is in an offside position, a clear offside position, maybe two metres. After that there's an offside position of influence as well because he's going to the ball.
"It's true, the defender touched the ball, but the defender touched the ball when the striker is going to press him and close to him."