On paper it is possible. But in reality, it is difficult. Barcelona is 9 points ahead of Madrid. Barcelona needs to lose their next three matches and Madrid needs to win their next three matches. Then the points of these two teams will be equal.
But Barcelona's only goal now is to secure the La Liga title. Even though several important players of Barcelona are injured, the Barcelona team is still stable. And Xavi will continue to do his best to secure the La Liga title.
Moreover, Real Madrid's performance in La Liga is not stable. They have dropped points in three of their last five matches. And they have drawn in the last two matches.
Don't forget that there is still the game between Real Madrid and Barcelona left. There is one game in between where Real Madrid faces Espanyol Barcelona and Fc Barcelona has to go to Athletic Bilbao. Hypothetically, if Real Madrid wins their game and Barcelona does not win (either draw or loss), the clasico could be an exciting game again as Real Madrid could come really close if they decide that match in their favor.
If Real Madrid can't reduce the distance within the next two games, then there will be 12 games left to make up for 9 points. I would say if Barcelona wins the clasico it is definitely over. 12 points and 12 games left, no chance that Barcelona let's that success slip out of their hands. 9 points would still need some magic to happen, but there is a slight practical chance if Barcelona ties a game and maybe loses another one pretty soon afterwards.