Perhaps the two sides were still feeling the effects of their midweek exploits as the game was extremely slow to catch fire. Vinícius Júnior was causing some early trouble for Athletic right-back Andoni Gorosabel, but it took until the 27th minute for him to worry Unai Simon.
The Brazilian wide man found space 25 yards from goal and unleashed a vicious effort that whistled just over the bar.
On the half-hour mark, Aitor Paredes had to be at full stretch to divert Eduardo Camavinga’s through ball away from its intended target of Rodrygo, shortly before Valverde flicked a header wide from one of five first-half corners that Los Blancos mustered without any real alarm for the visitors.
While they were largely untroubled at the back, Ernesto Valverde’s side had just 25% possession in the first half and only had Gorka Guruzeta’s mistimed acrobatic effort to talk about at the other end.
Carlo Ancelotti evidently had some stern words at the break as his side came out with a level of energy not seen in the opening period. Camavinga was leading the charge just two minutes in as he teed up Rodrygo to curl wide before seeing his effort after a strong run tipped over by Simon.
The Athletic goalkeeper then showed why he is Spain's number one with a stunning save to deny Jude Bellingham after he met Vinicius’ skilful cross with a strong header.
The Estadio Santiago Bernabeu erupted on 80 minutes when Vinícius finished clinically at the near post, but a VAR check showed that substitute Endrick had strayed a hair offside in the build-up, which summed up a frustrating night up to that point for the reigning champions.
Athletic have the best defensive record in LaLiga this season, and just when it looked as though they would keep out Los Blancos, Uruguay international Valverde smashed a looping volley into the top corner deep into stoppage time to cue bedlam.
After their humbling UEFA Champions League (UCL) exit to Arsenal in midweek and Barcelona’s thrilling victory on Saturday, the importance of this win cannot be understated.
They remain four points behind their bitter rivals at the top, but this will give Real confidence heading into next week’s Copa del Rey final and down the stretch in the league. Athletic will be disappointed with their 17th defeat out of 20 at the Bernabeu, but still look set for UCL football next season.
Flashscore Man of the Match: Federico Valverde (Real Madrid)