"It may be possible but it is very difficult, almost impossible," Ronaldo told reporters.
"I do not believe in miracles. Yes, you have to win to gain confidence for the Champions League and winning trophies always gives you confidence - this is the thought we must always hold on to.
"It's not about me - what matters is Real Madrid and continuing to win. Scoring goals is important but my priority is to help the team and that's my job. The team was playing well, I went on in the second half and tried to help with a goal and an assist."
Ronaldo scored his 29th league goal in Saturday's 5-1 win over Levante.