Madrid, July 4 (IANS): Former Atletico Madrid defender Tomas Ujfalusi on Saturday warned his ex-teammate David de Gea, saying the club's fans will not forgive the current Manchester United goalkeeper if he joins cross-city rivals Real.

De Gea has this week been seen here, increasing speculation he will leave United for Spanish football giants Real. The 24-year-old insisted he was there only to "relax', and "on vacation", but he is a target for Real, who rarely fail in their pursuit of players, reports dailymail.co.uk.

De Gea joined United from Atletico, where he started his career, for 18.9 million pounds in 2011. A year earlier he was a crucial figure as Atletico won the Europa League.

Czech international Ujfalusi was part of de Gea's defence that season and popular with the club's fans after spending three years in the Spanish capital; De Gea was equally liked, but Ujfalusi believes he will throw that away if he signs for Real because Atletico's fans would feel betrayed.

"No, no, no. They are not going to forgive him [if he joins Real Madrid]. It's not going to be easy for him to make this decision, for sure," the retired defender, who played 92 matches for Atletico, said.

"It's also a surprise for me because he's an Atletico Madrid fan - when he was young his heart was with Atletico Madrid."

De Gea initially struggled when he arrived in Manchester as the retired Edwin van der Sar's successor. The pressure could be even greater at Real -- where he is seen as the long-term replacement to Spanish icon Iker Casillas for both club and country -- but Ujfalusi has complete confidence in his ability to succeed.

When the former Czech Republic international left Atletico in 2011, Thibaut Courtois was arriving on loan from Chelsea. He also won 78 caps playing alongside compatriot Petr Cech with the national team.

Few, therefore, are in a position to judge three of the world's best goalkeepers in such depth, but there is little doubt about who he believes is best.

"I have to say De Gea (is superior to Cech and Courtois). I was working with him for more than two years, and he was playing really well," Ujfalusi, 37, said.

"It's difficult to say, but Petr Cech is 10 years older than de Gea and Courtois. The beginning in Manchester United wasn't so easy for him, but I think now he's back in his old form and playing very well."