Real Madrid's game against Ossasuna will take place slightly later, on Tue 19th, but there's seems to be some controversy with that game. Apparently Real and Atletico had an agreement with the Association of Spanish Footballers that, should any of them reach the quarter-finals of the FIFA Club World Club, their opening La Liga games would be postponed to later terms. But, despite Real reaching the semi-final, La Liga president, Javier Tebas has stated that Real's request to postpone the game was officially rejected.
More info here:
https://www.goal.com/en-us/lists/real-madrid-xabi-alonso-massive-blow-la-liga-opener-against-osasuna/blte9c595784207f1d3First off, the players health should matter when considering the fixing of these competitions and games however Laliga’s decision not to postpone Real Madrid’s season opener shouldn’t be much of a problem since their elimination from the club world cup came much early and so they still have a bit of time to prepare for the next season.