The 27-year-old was decisive for Los Blancos as his fourth goal in his last five appearances against Pep Guardiola's men sealed all three points for his team, and Jose Mourinho's assistant feels his tendency to rise to the occasion separates him from his contemporaries.
"For me, Cristiano is the best player in the world. He has given us some of our greatest moments. Back in [last season's] Copa del Rey final, he gave us the title," Karanka said after the match.
"Ozil also played well tonight. These are three important points that give us confidence to continue working hard."
The victory means Madrid now move seven points clear of Barca at the Liga summit with only four matches left, and are now overwhelming favourites to lift their first Primera Division title in four years.
However, Karanka insists Saturday evening's win at Camp Nou has not decided the outcome of where the trophy will end up, and urged the side to begin focusing on Wednesday's Champions League semi-final second leg against Bayern Munich, as they aim to overturn a 2-1 deficit.
"The league is not decided yet. There are other matches left and we have to continue working hard," he continued.
"The fans are happy with the work of this team. Now we have to focus on our Champions League match."
"We have to make a comeback against Bayern. We already know what the atmosphere will be like at the Bernabeu."