Isco scored a brace in the Saturday's 3-2 win over Sporting Gijon. Getty

Zinedine Zidane has refused to confirm whether Isco will start against Bayern Munich on Tuesday night (18 April), after the injury of Gareth Bale has left a place available in his Real Madrid line-up. Meanwhile, Cristiano Ronaldo, Karim Benzema, Keylor Navas and Dani Carvajal return to Los Blancos' 19-man squad after being rested during the weekend's 3-2 win over Sporting Gijon.

Isco, 24, led his side to the victory over the Asturian side by scoring two goals after Zidane gave an opportunity to his fringe players in order to have his key players fresh for a crucial week which will see Bayern and Barcelona visiting the Santiago Bernabeu in the space of six days.

Real Madrid fans and pundits hoped Isco's performance – alike with the injury of Bale – would be enough to see their favourite midfielder starting against Bayern Munich on Tuesday night. However, James Rodriguez, Marco Asensio or Lucas Vazquez are also vying for the role and Zidane refused to confirm who will be the chosen one to fill the gap left by Bale's absence.

"Isco is ready (to play) like everyone," Zidane said in the press conference ahead of the game. "That's the most important thing for me. Tomorrow we'll decide who plays and how we're going to play."

Isco has voiced his frustration over the situation in recent times as he has only played 77 minutes of Champions League football in the current season.

The former Malaga star has even refused to sign a new deal at the Santiago Bernabéu despite his current contract being set to expire at the end of next season – with some reports in Spain even linking him with a shock move to Barcelona.

Zidane has reiterated in recent weeks that he wants Isco to continue but asked whether he has spoken with the midfielder to convince him to sign a new deal, he replied: "No, I haven't spoken to him."

"[His lack of playing time is a] coincidence, but due to rotations, he's not played much in the Champions League. We have a lot of important games and we'll see what we do tomorrow. I have decided who plays but I'll not say. Everyone is doing phenomenally well, but I have to choose and I'm glad that everyone is at this level. It's better to have this problem when having to choose the team."

The Real Madrid boss will have fewer problems to form his defence as Raphael Varane and Pepe will continue on the sidelines for both the visit of Bayern and El Clasico against Barcelona. Sergio Ramos and Nacho are thus his only two centre-backs available and will continue in the heart of the back-line alongside Dani Carvajal and Marcelo.

Los Blancos have a 2-1 advantage after Cristiano Ronaldo scored a brace in the reverse fixture played at the Allianz Arena last week. Zidane warned about the potential of Carlo Ancelotti's side but hopes that the result at Bayern and the support of the Santiago Bernabeu will help his side to secure the qualification for the semi-finals of Champions League.

"You know the importance of the match tomorrow and our fans will be more important than ever. We always need them and they're always there, but in this type of game we ask that they're with us all the way and that they're the extra man. The fans at the Bernabéu always give us an advantage and even more so in important matches like this," the Real Madrid boss said. "We have to have a great game and be very strong. We will go out to win the game and we'll not gamble. The first leg has already been played and we know the problems Bayern will create, they'll make it difficult until the referee blows for full-time. We're going to have to play really well. We must do everything we can to win the game."

Bayern are expected to recover Robert Lewandowksi after the club's top scored missed the first leg due to an injury in his shoulder. Zidane has admitted that the return of the Poland international would be an added concern for Real Madrid but backed his defence to cope with it.

"Lewandowski is a real number nine and a bonus for Bayern," Zidane admitted. "Bayern have a great team in all departments so we have to be focused on what we have to do. We know that they have a lot of ways to cause problems for their opponents and they also have flaws. We'll try to play our game and prepare the game well. The result of the first leg does not ensure anything and we must have another great match. It's going to be a great game. It will be decided by small details and we must be ready."