Why it's impossible? in La Liga there are many clubs, not only Girona and Real Madrid. If Girona lose against Real Madrid, but win the rest of the matches, there's a possibility Girona can become a champion since Real Madrid will not always able to win against other clubs.
Barcelona is the example, they can become a champion in the last season when they're sometimes lose against Real Madrid.
This is called competition. There will be a match that they have to carry out and at the end of the championship determination is not just one game. No one can predict, but with the calculation of the points difference, the hope will be wider, Real Madrid can stay until the end of the season and make no mistakes. What is needed right now against girona is a win and 3 points. Because it will add a safe distance if Madrid make one mistake in the rest of the game.