The Portuguese suffered a minor knee injury in the midweek win over Borussia Dortmund and will undoubtedly be missed for the trip to Anoeta
Real Madrid's La Liga title chase takes them to Real Sociedad on Saturday, but trips to Anoeta have proved fruitless for many this season.
Carlo Ancelotti's men bounced back from back-to-back league defeats with a 5-0 demolition of Rayo Vallecano last weekend, before cruising to a 3-0 win against Borussia Dortmund in the first-leg of their Champions League quarter-final tie in midweek.
They sit third in the three-way battle for the title, three points behind leaders Atletico Madrid and two adrift of Barcelona, but Sociedad are a difficult nut to crack on home soil this season, having lost just two of 15 league fixtures in front of their own fans.
Barca and Athletic Bilbao are among those sides to come away from Anoeta empty-handed so far this term, as Sociedad continue to eye Champions League qualification for a second successive season.
Jagoba Arrasate's charges are six points short of fourth-placed Bilbao, with seven matches left to play, and will take confidence from their 3-3 draw against the men from the Spanish capital in this fixture last year.
Cristiano Ronaldo was booed by his own supporters during last week's win over Rayo, but showed few ill effects as he regained their backing by finding the net in his 100th Champions League appearance on Wednesday.
The Portugal captain was, however, withdrawn by Ancelotti 10 minutes from time, although the Blancos boss has since moved to allay fears of a serious knee injury, calling the problem a "minor annoyance", though the 29-year-old will be out of Saturday's match.
Xabi Alonso stressed that the team would not favour the Champions League over La Liga, adding: "It's not a question of choosing; you have to fight for everything and we have a great opportunity in all competitions.
"In the Liga we are doing better than last year."
Madrid are likely to have to do without the services of Marcelo once again after the full-back was confirmed to be suffering from a torn hamstring earlier this week.