The Blues boss dropped the 6ft 8in Serbian striker for Saturday's 4-0 defeat to Watford following his dismal efforts in training.
But he made a positive return to action after enjoying a busy evening, despite missing more than his fair share of opportunities, not least when he failed to anticipate Chris Burke's cross and diverted the ball wide from merely four yards out with time running out.
"Nikola's response was fantastic, absolutely brilliant," Clark said.
"I spoke with him on Monday morning and the two things I said were, I think he's an extremely talented footballer, and I've got a lot of respect for him as a guy.
"But he has to understand I've got my principles, my standards, my rules. As I said, there was no rant, no shouting, it was me just making a decision I felt was right.
"It's gone now. He's responded in the right way, he's put in a terrific 94 minutes for us - work ethic, quality on the ball, I'm just disappointed for him he didn't get the goal his performance probably deserved.
"He showed me by his performance he hears what I'm saying and he's gone about his business in the right and proper way.
"He's showed tonight he's not just big in size, he's a big man as well."