Real Madrid 's 4-3 loss to Schalke has prompted further calls for change in the Spanish capital . They progressed to the quarter-finals of the Champions League thanks to a 2-0 win in the first leg , but Tuesday night was supposed to be easy . On Sunday , their place at the top of La Liga was swiped from underneath them , and 92 % of fans have demanded a change in tactical approach , according to a recent poll in AS . Most players have been criticised - Cristiano Ronaldo included - but perhaps most under-fire is Iker Casillas . Mr Real Madrid , with over 500 appearances . Real Madrid goalkeeper Iker Casillas has come under heavy scrutiny after a series of poor performances . Manchester United goalkeeper David De Gea has been touted as the perfect replacement at Real Madrid . Three of Schalke 's four goals could have been saved , they said . Casillas needs to leave , they said . At 33 years of age , he may well be past his best , with three European Cups , five league titles and one World Cup tucked safely under his belt . Manchester United 's David De Gea has been touted as his possible replacement , and even Sportsmail 's Jamie Carragher waded into the debate on Tuesday night . 'Madrid need a new keeper . De Gea wants to win trophies . No brainer , ' he wrote on Twitter . De Gea was labelled the best goalkeeper in the world by Roy Keane this week , and may leave United . Keylor Navas is also waiting for his chance at the Bernabeu after joining in the summer . And perhaps he has a point . Manchester United have fallen short of expectations once more , and De Gea will be keen to taste success ... where better than the city he was born ? He is a Spain international , and certainly talented enough to take the reins from his countryman . But you get the feeling that Real Madrid would not be the same without Casillas . Since 1999 , he has been a main-stay at the Bernabeu . At the end of the game on Tuesday night , there was an endearing moment in which he refused to let his team-mates leave the pitch before thanking the Madrid fans . Casillas would not let his team-mates leave the pitch on Tuesday night before they thanked the supporters . Cristiano Ronaldo was unhappy at his side 's performance , but was made to applaud the fans by Casillas . Pointing and pulling , ushering his team-mates to the corners of the pitch to applaud the supporters . But still they want rid . For the first goal , he palmed the ball into his bottom corner . For the second , he pushed it into the path of Klaas-Jan Huntelaar . For the third , he was rooted to the spot . Success is in Madrid 's nature , and their fans are n't happy with the amount of goals they are conceding . That starts at the back ... with Casillas . Aside from De Gea 's potential arrival , you ca n't forget the presence of Keylor Navas . Signed from Levante in the summer , he is waiting , willing , wishing for his chance . De Gea is a Spain international and grew up in Madrid , playing for Atletico before moving to Man United . Casillas has had a remarkable career , winning numerous trophies including the 2010 World Cup . But De Gea makes sense . He is 24 years old , and getting better with every game he plays . Signed by Sir Alex Ferguson for just shy of £19million in 2011 , United would make a tidy profit on him if he were to leave . ' I think David De Gea is the best goalkeeper in the world at the moment , ' Roy Keane told ITV after Monday night 's FA Cup clash with Arsenal . The best goalkeeper in the world to one of the best football clubs in the world . Maybe Jamie Carragher has called it right again .
Real Madrid lost three-3 to Schalke in the Champions League on Tuesday . Iker Casillas came under fire after being at fault for 4 of the goals . Jamie Carragher believes David De Gea would be the perfect replacement . Casillas has made over 500 appearances for Real Madrid since 1999 . CLICK HERE for all the latest Real Madrid news .