Barcelona lie in wait for the winners of this tie after they overcame Real Sociedad on penalties after a 1-1 draw in Wednesday's semi-final.
Real Madrid's La Liga showdown with Osasuna was given the go-ahead despite the widespread disruption caused by Storm Filomena, and the La Liga champions could not get back on their perch in freezing conditions at the El Sadar Stadium.
Despite enjoying 70% of the possession, Real Madrid could not find a way through and ultimately claimed a point from their trip to Osasuna, and the decision to play the match did not sit well with Blancos goalkeeper Thibaut Courtois, who blasted the authorities for their decision not to postpone the game with Storm Filomena raging.
League leaders Atletico Madrid did see their match postponed, though, and Real Madrid would have usurped their local rivals in the table with a win, but that goalless stalemate ensures that Atletico remain one point clear of Zinedine Zidane's men with three games in hand.
However, that result saw Los Blancos extend their unbeaten run across all competitions to nine matches - with seven of those games ending in wins - and Zidane's men will be determined to retain their Supercopa de Espana crown after beating Atletico in last year's final in Saudi Arabia.
Only Barcelona (13) have won the competition more times than Real Madrid (11) since its inception, and Los Blancos will be making their 17th appearance in the Supercopa when they take to the field against a well-rested Athletic.
Athletic were due to take on table-toppers Atletico at the weekend, but a heavy snowstorm prevented the plane carrying Marcelino's men from landing safely in the Spanish capital and that game was indeed postponed.
As a result, Marcelino's wait for his first win as Athletic boss goes on after he oversaw a 3-2 defeat to Barcelona in his inaugural game in charge - a result which left Los Leones nine points adrift of the top six amid their inconsistent form.
Only two of Athletic's last nine matches have ended with the Supercopa semi-finalists taking all three points, and while Marcelino's side will begin their 2020-21 Copa del Rey campaign next week against Ibiza, they are still waiting to play last season's final with Sociedad following the chaos caused by the coronavirus pandemic.
Athletic have lifted the Supercopa de Espana trophy on two occasions in 1984 and 2015, with Barcelona falling victim to a 5-1 aggregate defeat to Los Leones in the latter year.
December's battle between Real Madrid and Athletic ended with the La Liga champions cruising to a 3-1 victory, and Zidane's men have not lost to their semi-final opponents since the 2014-15 campaign.
Real Madrid form (all competitions): WWWDWD
Athletic Bilbao form (all competitions): LWDLWL
Real Madrid defender Dani Carvajal would have been eligible to play this match after serving a suspension against Osasuna, but the Spaniard is expected to miss out here with a muscular injury.
Athletic have a couple of injury concerns to contend with as well, starting with left-back Yuri Berchiche, who is a major doubt after being forced off in the first half against Barcelona with a thigh problem.
Yeray Alvarez could be given the green light to return here but it would be a surprise to see him risked from the first whistle, so Unai Nunez should keep his place alongside Inigo Martinez in the heart of defence.
Real Madrid possible starting lineup:
Courtois; Vazquez, Ramos, Varane, Mendy; Casemiro, Kroos, Valverde; Asensio, Benzema, Hazard
Athletic Bilbao possible starting lineup:
Simon; Capa, Nunez, Martinez, Balenziaga; De Marcos, Vesga, D. Garcia, Muniain; Williams, R. Garcia
We say: Real Madrid 2-1 Athletic Bilbao
Marcelino's Athletic gave Barcelona a terrific run for their money and will be hopeful of welcoming a couple of players back from the infirmary after a week-long break. However, Zidane will be desperate to guide his team to silverware in a bid to further ease some of the pressure on his shoulders, and Los Blancos are not expected to cruise to victory by any means, but they should do enough to book their spot in Sunday's final.