During the 2010–11 pre-season, Real Madrid's first-team coach, José Mourinho, said:
It's a shame Mateos can't join us because I like him a lot. He defends well and knows how to instigate play from the back. That's a trait which we need here at Madrid. With the difficulties we have it is a pity that he can not play, I would like him to be part of the first team.[5][6]
The coach's statements instigated Real Madrid to sign the player to a professional contract[7] and, subsequently, Mateos was called for the first match of the campaign against Mallorca.[8] After the departure of Rafael van der Vaart and Royston Drenthe, to Tottenham Hotspur and Hércules respectively, he was promoted to the first team, being awarded the number 15 shirt previously worn by the latter.[9][10]
Mateos made his official debut for Real Madrid on 23 November 2010, playing ten minutes in the 4–0 away win over Ajax in the group stage of the UEFA Champions League; after the match, he said: "I will never forget this day."[11] His last competitive appearance came the following 6 January when he started the 2–0 loss at Levante in the round of 16 of the Copa del Rey,[12] with his side eventually claiming the trophy.[13]
On 29 January 2011, AEK Athens signed Mateos on a six-month contract with the option of retaining the player for an extra year.[14] In the summer, however, he moved to Real Zaragoza also on loan for one season,[15] making his top-flight debut on 11 September in a 0–0 draw at Rayo Vallecano,[16] but the spell was marred by injury.[17][18]
In June 2012, Mateos accepted a return to Castilla for 2012–13, as the reserves had promoted to Segunda División after an absence of five years.[19]
Ferencváros
On 2 September 2013, Mateos signed for Hungarian club Ferencváros.[20] He scored two goals in 21 games in his first season, helping his team to third position.
Orlando City
On 29 July 2015, Mateos joined Orlando City of the Major League Soccer, with general manager Paul McDonough describing him as a "well-versed" player who he expected to "make an impact right away".[21] He was waived on 3 March 2017.[22]
Murcia
In August 2017, Mateos signed for Spanish third-tier Real Murcia.[23] He scored his sole goal on 17 March 2018, opening an eventual 2–1 away defeat of Granada B.[24]
^"Mateos aláírt" [Mateos signed] (in Hungarian). Ferencvárosi TC. 2 September 2013. Archived from the original on 5 September 2013. Retrieved 2 September 2013.