The Spanish outfit are currently third in Group B with just seven points taken from their opening five matches.
However, they still find themselves able to qualify for the last 16 due to how closely contested the group has been so far.
Should they defeat Gladbach, they will move on to 10 points and finish in the top two.
They could also potentially qualify with a draw, but only if Inter manage to defeat Shakhtar in the other game in the group, but Casemiro says a win in their own match is the only thing Madrid are focusing on.
"We know that tomorrow is the most important game of the year," the Brazilian said in the pre-match press conference.
"We all know that tomorrow is a final. We have to face it as if it were a final."We've been taught at this club that you don't play finals, you win them. We're not thinking about anything other than winning.
"We know there is a good opponent and they're top of the group, so we have to respect that. But, we're going out to win."
Champions League Group B
|3. Real Madrid||5||2||2||7|
Casemiro also took time to defend under-fire head coach Zinedine Zidane, who has been criticised for his management of the club this season, particularly as they struggle in Europe.
"What am I going to say about Zidane? He has made history, last year he won two trophies. Many times we don't realise what Zidane has done," he said.
"The season is strange, it's true. The pre-season was not good and playing every two or three days is difficult. The team is with the coach. And I value what he has done and what he is doing."
Madrid aren't doing much better domestically, as they are currently six points adrift of leaders Atletico, having also played one game more than their city rivals.