Real Sociedad relied on their defense, but against an attack like Real's, it is very difficult to do. After the goal conceded, it was difficult to change strategy, although they had enough time, but they could not do anything, so Real gets an important victory. Ancelotti made a small rotation for this match, but this did not help Sociedad either, although they had several good attacks, Real's defense played this match perfectly.
Indeed, basically Real Sociedad has lost in everything so it is difficult for Real Sociedad to lose to Real Madrid even though Ancelotti has made some rotations but it does not have a big effect on Real Madrid's performance.
It must be admitted that Real Madrid's strength is much stronger and indeed there are no surprises that occur in this match and it is almost certain that Real Madrid can advance to the final round of the Copa Del Rey this season because the second leg later Real Madrid will play at home with an Agg advantage of 1 goal of course it will make it easier for them.