Despite being less convincing so far this campaign, Solari feels Madrid can make it four in a row in 2019.
Asked what came to mind when he thought of the challenge of winning a fourth straight title, the head coach told UEFA: "That nothing is impossible for Real Madrid."
Madrid's first step in the knockout stage is Ajax, with the first leg of their last-16 tie to be played in Amsterdam on Wednesday.
Solari knows the challenge awaiting Madrid against the Dutch giants, who last won the competition in 1995.
"That's the way they still work, with a team that has already shown that it was competitive last year and that it remains competitive this year.
"The tie is going to be difficult, like all these occasions in the Champions League."
The club currently six points behind rivals Barcelona following the leaders' scoreless draw with Athletic Bilbao on Sunday