Kovacic and Erling Haaland struck for City's 2-0 win on Sunday night.
He later said: "We are missing some big players but it's always tough when you miss big players.
"I had a longer break so I could recover better, I wanted to be ready for the beginning of the season."
On Rodri's absence, Kovacic also said: "I play today some kind of his role, but we are always missing Rodri because he is, if not the best player, one of the best in the world.
"I don't score many goals and when you score you want to celebrate. But I have a huge respect for Chelsea, I spent five years here.
"I scored but that is not always the most important thing for me, the most important is winning.
"This team is so hungry and it's a pleasure to be a part of it and win titles."