Real Madrid have hit a tumbling block in their pursuit of Sergio Aguero after Manchester City informed the Spaniards they're unwilling to do business, while Keylor Navas is calm on his future at the Bernabeu.According to Spanish newspaper AS,via talkSPORT, Manchester City are unwilling to enter into negotiations with Rafa Benitez's side and are even looking to extend Aguero's contract.The Argentina striker is currently on international duty at the 2015 Copa America, where Gerardo Martino's side are expected to go far as one of the tournament's favourites.Spanish dailySport provides further detail on just how highly the 2013-14 Premier League champions value Aguero, saying the club will offer him a "blank check" in order to keep him happy:Benitez currently has Karim Benzema leading his attack, but Los Blancos may be expected to excite their fans in the summer transfer market after failing to claim a trophy this season.Aguero bagged 26 goals in 33 Premier League games last season to claim the Golden Boot Award, a small consolation after failing to retain City's Premier League crown.Most clubs would be forced to bend to Real's will once the La Liga titans decide a player is on their wanted list, but City are in the position of being able to battle with the club in a financial sense.It's no surprise the Citizens have come upon consistent domestic success since Aguero arrived at the Etihad Stadium in 2011, winning two Premier League titles, a League Cup and the Community Shield in the past four years.Considering the striker plays such a fundamental role in their line-up, it's of little surprise to see City issue a hands-off warning on Aguero as they seek to see him further imprint his name in the club's history books.Navas Unfazed by De Gea SpeculationAll talk of a potential David De Gea arrival at the Bernabeu isn't bothering Real Madrid incumbent Keylor Navas, who has admitted he'll take the future as it comes.ESPN FC's Dermot Corrigan cites reports in Spain suggesting Iker Casillas could be sold this summer and replaced by Manchester United stopper De Gea, but Navas is only concerned with his own progress. He told AS:You cannot talk about the future, as nobody knows it yet.But I have a contract with Madrid, I am Madrid's goalkeeper and I am happy and proud to be at this great club.I am relaxed, I work with humility, I do not know any other way. I have confidence and ability to do well. I trust in myself, and many people also trust in me, which I appreciate.Navas' comments came in the wake of Costa Rica's 2-1 defeat to Spain, where, despite his inferior concession rate to opposite number De Gea, the 28-year-old made some sensational stops.AS were one of the first in line to congratulate Real's reserve goalkeeper for his performance in the friendly fixture, where Costa Rica were fortunate not to have finished on the end of a bigger deficit:New manager Benitez may respond positively to Navas' calm demeanour, hinting that he may be willing to fight De Gea for the starting berth next season if Casillas is indeed moved on.Navas made only 11 appearances across all competitions last season, having arrived in Madrid after the 2014 World Cup for a fee of 10 million.Despite that lack of first-team playing time, the Costa Rica No. 1 is still regarded as an elite stopper to many, with a long summer lying in wait for the Real Madrid goalkeeper ranks. Click here to read full news..