Diego Maradona has advised Manchester City striker Sergio Aguero to transfer to Real Madrid in the summer."'El Kun' [Aguero] has to play for Real Madrid. If he does, he can make the next step in his career," the Al Wasl coach told Argentine radio station Radio La Red.The Argentine legend is of the opinion that the 23-year-old can reach the next level in the Spanish capital club, adding that Los Blancos' president, Florentino Perez, has "no limits" and could bring his son-in-law to Jose Mourinho's team despite resistance from the English club.Maradona went on to say that Aguero should have joined Madrid instead of Premier League leaders City last summer."Although City are flourishing now, it would have been better for him to sign for Madrid. He made a mistake," Maradona explained. "Now that City are doing well, it will not be easy to take him away from them. They will want to keep him, because Mancini plans with him in mind.He added, "In any case, if Madrid want someone, they get him. Florentino has no limits. If 'Kun' were playing in Madrid, he would help trim the advantage of Barcelona."Maradona went on to theorize that Portuguese ace Cristiano Ronaldo could reach new heights if partnered with the 23-year-old forward."We would be talking of Cristiano Ronaldo scoring over 60 goals, because Aguero would draw the whole opposing defense," the 51-year-old argued.