Real Madrid coach Zinedine Zidane on Wednesday confirmed that he has signed a contract extension which will keep him at the European champions until 2020.

"It's signed," said the French star after his side drew 2-2 with Numancia to progress to the quarter-finals of the Copa del Rey 5-2 on aggregate.

After a dream start at Real, with eight trophies out of a possible 10, Zidane has endured a tough season with his side 16 points behind Barcelona in the La Liga title race.

And the 45-year-old cautioned: "I'm enjoying what I do every day, because that's the way it is. I can't imagine myself as a coach in two, three years, because things are not like that.

"I know how it goes, nothing more, even with this contract it does not change anything."

On Wednesday, Real fielded an almost unrecognisable team and struggled into the Copa del Rey last-eight.

Zidane could afford to rest his superstars with one eye on La Liga and the Champions League last 16 with a clash against Paris Saint-Germain next month.

However, they were far from convincing at the Bernabeu.

Lucas Vazquez scored both of Real's goals after the 11th and 59th minutes.

But on both occasions, their modest visitors fought back thanks to a brace from Guillermo on the stroke of half-time and then after 82 minutes.

Numancia ended the game with 10 men after captain Dani Calvo was red-carded in the dying moments.

Leganes, a modest club from the Madrid suburbs, reached the quarter-finals of the Copa del Rey for the first time in their 89-year existence.

Despite losing 2-1 at Villarreal, who are currently sixth in La Liga, Leganes progressed on away goals having won the first leg 1-0.

Moroccan international Nabil El Zhar scored the crucial away goal for mid-table Leganes on the half-hour mark.

In the night's other early second leg tie, last season's runners-up Alaves downed third division Formentera 2-0 for a 5-1 aggregate win.

On Thursday, three-time defending champions Barcelona host Celta Vigo with the two sides locked at 1-1.

Barca coach Ernesto Valverde insisted that despite the high-profile capture of Philippe Coutinho, who can't play for around three weeks due to a thigh injury, his team's character will not change with the Brazilian's arrival.

"The Barca model will stay the same," he said Wednesday.

"The club always has the chance to go into the market to buy the great players. But at the same time, Barca will continue to nurture young players at the training centre to maintain the style and identity.

"That's still the case today."