City claimed a stunning 4-0 victory over Monchengladbach in their Champions League opener on Wednesday night and the star of the show for the Citizens was unsurprisingly Aguero, who managed a wonderful hat-trick on the night.
Following the game, Gladbach loanee Christensen was left in awe of Aguero and admitted that the striker was impossible to stop during the encounter.
The 20-year-old said: "He's hard to stop. He is smart. We did our best, but he is always dangerous. It's difficult as he is clever, he always tries to be one step ahead of the defence.
"We were completely ready at the start, so it had nothing to do with it. At times we actually played the game we wanted to, but otherwise there's not much we can take from this match."