"We are looking at our options because we are without Javier," he said.
"It is a blow to be without Mascherano because he has been playing very well, but I am sure we will be able to choose a very good player to take his place.
"Lucas is a young player who can be an option, but there is also Crouch and Voronin who have both been training well. I have a lot of confidence in Lucas, or Crouch or Voronin if we want to change the system. I don't think it will be a problem but we will lose something.
"Lucas can come in for Mascherano. He played well against Inter Milan, so why can he not play well against Everton? He can do the job.
"It is a very big game for both clubs, firstly because we are local rivals and there is a lot of pride at stake, but also because we are both looking to get fourth position.
"Everton have won a lot of games this season and are near the top of the table so we know that they are having a good season.
"We need to look to play well and I am sure it will be an exciting spectacle for everyone.
"But even if we do win I do not think it will mean that the battle for fourth place is over because we will have to go on and win more games in a row.
"Finishing fourth is always important for every club. We know what Champions League means in terms of money and also for the name of the club. It is really important.
"If we win the Champions League then we have qualified again. If someone offered me that I would take it, but it is important to be sure you will be in the top four. In the Champions League you never know what can happen."