Real Madrid threw away a two-goal lead but eventually triumphed 5-2 after extra time against Celta Vigo on Thursday to reach the Copa del Rey quarterfinals, with youngster Endrick netting twice.

On the back of a humiliating 5-2 Clasico defeat of their own by Barcelona in the Spanish Super Cup last weekend, Madrid seemed to be heading for a relatively serene triumph before two late Celta goals forced extra-time.

Madrid players and coach Carlo Ancelotti faced whistles when they walked out after the defeat in Saudi Arabia and it was harder than expected for them to book a place in Monday's draw for the last eight.

Kylian Mbappe scored a brilliant opener before the break, although Celta complained vigorously over what seemed a sure penalty in Madrid's area moments beforehand.

Vinicius netted early in the second half to help Madrid take control, but Jonathan Bamba's late goal gave Celta hope in the final stages.

Marcos Alonso stroked home from the penalty spot after Bamba was fouled in stoppage time to force extra-time.

Teenager Endrick put Madrid ahead again, Fede Valverde powered home their fourth and Endrick struck once more with a clever backheel to wrap up the win, which was entertaining but did little to ease concerns over their defensive frailties.

One of the few positives Madrid took from the Super Cup defeat was Mbappe's goal and performance in Jeddah.

The former Paris Saint-Germain star looked back to his best and again impressed for Madrid after a shaky start to life in the Spanish capital.

Mbappe took the opening goal brilliantly, although it was mired in controversy after Madrid goalkeeper Andriy Lunin appeared to bring down Williot Swedberg in the area.

The referee gave nothing and Madrid countered, with Mbappe zipping past a defender and finishing with aplomb.

Celta hoped VAR would instruct the referee to view the penalty claim again but no such instruction followed and Mbappe's goal stood.

HOLDERS BILBAO CRASH

Vinicius added Madrid's second goal early in the second half with a cool finish after Mbappe and then Brahim Diaz combined to set him up.

Celta opened up in search of a way back in and Madrid created several more clear chances.

Mbappe headed over from close range from Diaz's cross as Los Blancos found their flow, without being able to add to their lead.

Carl Starfelt cleared off the line for Celta after Vinicius lobbbed goalkeeper Ivan Villar in search of the third.

At the other end Lunin tipped over a long range effort from Hugo Sotelo to keep the Galicians at bay.

Madrid substitute Arda Guler stroked home for the hosts but the goal was disallowed for offside against Vinicius in the build up.

Celta pulled one back in the 83rd minute after Eduardo Camavinga foolishly gave the ball away on the edge of his area and Bamba struck to create a tense finale.

The visitors got their reward when Raul Asencio clumsily bundled down Bamba in the area and Alonso dispatched the penalty into the bottom right corner to take the game to extra-time.

Madrid's 18-year-old Brazilian striker Endrick, hungry for opportunities, blasted home from the edge of the box to put his side ahead after 108 minutes.

Valverde slammed an unstoppable effort from 25 yards out past the helpless dive of Villar to extend Madrid's advantage.

Endrick wrapped up the Spanish and European champions' triumph with an improvised backheel finish from close range.

Earlier Osasuna knocked out cup holders Athletic Bilbao with an entertaining 3-2 win at the San Mames, while Real Sociedad ousted Rayo Vallecano with a 3-1 victory.

Barcelona and Atletico Madrid secured progress to the last eight on Wednesday.