Los Blancos have shared the points in two of their last three matches, including a disappointing goalless draw away to struggling Osasuna in La Liga on Saturday.
The winner of Thursday's second semi-final will take on either Barcelona or Real Sociedad in the final of the competition on Sunday.
Here, Sports Mole rounds up Madrid's latest injury and suspension news ahead of the clash with Athletic, who saw their clash with Atletico Madrid on Saturday postponed due to bad weather.
Type of injury: Thigh
Possible return date: Unknown
Rodrygo Goes had to be stretchered off the field against Granada on December 23 after picking up a thigh problem, and the Brazilian is now facing an extended period on the sidelines, possibly as long as three months.
Status: Major doubt
Type of injury: Muscle
Possible return date: January 14 (vs. Sociedad)
Luka Jovic was ruled out of Saturday's clash with Osasuna due to a muscular issue, and the Serbia international remains a doubt for the semi-finals of the Spanish Super Cup.
REAL MADRID'S SUSPENSION LIST
Dani Carvajal was banned for Saturday's clash with Osasuna following his booking against Celta Vigo, but the right-back is available for this contest, and Madrid do not have any other suspension issues.