With a gap of 7 points if Barcelona wins until the last minute against Leganes, then the Real Madrid players who will be trusted by Ancelotti to play against Deportivo Alaves must work hard so that the gap with Barcelona does not become 7 points.
Barcelona won the match against Leganes. They are leading with 7 points now. Yes, Real Madrid must win the match against Alaves if they want to keep joining the race for the title. If they lose the next match, Barcelona will be closer to the La Liga title this season. There is no choice, Real Madrid must get 3 points in the next match.
We cannot deny that Real Madrid's current situation requires extra energy in pursuing trophies at the end of the season. After the match against Deportivo Alaves, Real Madrid must welcome the arrival of Arsenal. Against Alaves, of course, you have to be careful not to get injured.
Furthermore, Real Madrid will face Barcelona in the Copa del Rey Final. The time gap is quite close. Stamina is clearly drained.
Some teams have the same condition as Real Madrid. And it is not the first time that Real Madrid must face this condition. I am sure Real Madrid will have no problem to play against Alaves, it is just a small team. Ancelotti probably sends some key players on the bench. Sure, it is needed to anticipate the decline of Real Madrid players' stamina.