He emerged through Real Madrid's youth ranks, but made a name for himself in La Liga with Getafe, following which he returned to his previous team, winning two major titles but being sparingly played over the course of three seasons.
Granero represented Spain at under-21 level, appearing in the 2009 European Championship.
Born in Madrid, Granero joined ranks of Real Madrid when he was just eight years old, and quickly began displaying his footballing talent. In one season, he scored 83 goals in the under-10 division and, in 1999, captained the under-12 B-team that won the International Football-7 tournament held in the Palau Sant Jordi in Barcelona by defeating FC Barcelona 1–0 with his extra time goal – he was also named the best player of the competition.
Granero, alongside teammates Juan Mata and Alberto Bueno, won the Copa de Campeones Juvenil de Fútbol in 2006, an under-19 official youth tournament organized by the Royal Spanish Football Federation. He then joined the club's C-squad at the age of 17, standing out for his talent and passing skills and going on to receive the Números 1 Don Balón award as the "Most Valuable Player" of the fourth division Group 7 in 2005–06, an accolade bestowed by Don Balón magazine, one of the founding members of European Sports Magazines; that same season he made his first appearance with Real Madrid Castilla in a match against Albacete Balompié, during which he had a goal assist.
Granero made the definitive jump to Castilla in 2006–07's Segunda División, and slowly earned the confidence of coach Míchel until finally becoming an unquestionable starter. He would eventually fail to make the transition into the first team, as fellow cantera players Rubén de la Red, Javi García and Adrián González and, on 31 August, the last day of the transfer window, he moved to Getafe CF (also in Madrid) on a one-year loan; de la Red also joined Getafe, albeit in a different deal.
After the season's end, in which both he and de la Red were instrumental in the team's campaign, which included a quarterfinals run in the UEFA Cup, Granero returned to Real Madrid. However, on 13 July 2008, he joined Getafe permanently, with Real keeping a re-buy option on the player.
On 21 July 2009, Real Madrid exercised their buyback option in a reported €4 million deal, and Granero scored three goals during the pre-season. His first official one came in his first start, the opener in a 3–0 La Liga away success against RCD Espanyol on 12 September 2009. In his first season, where the Merengues eventually came out empty in silverware, he alternated the bench with starts, with irregular performances.
In the 2010–11 season, after Real Madrid purchased two players in similar positions, Sami Khedira and Mesut Özil, Granero was limited mainly to substitute appearances. On 16 January 2011 he came from the bench to score against UD Almería, in a 1–1 away draw against the bottom-placed team.
Granero's situation became worse in the 2011–12 season, with even Fábio Coentrão – another compatriot of manager José Mourinho who was signed in the off-season, originally as a left wingback – being preferred over him as central midfielder.
On 30 August 2012, Granero signed a four-year contract with English club Queens Park Rangers after transferring for a reported fee of £9 million, and was handed the number 14 shirt. He made his Premier League debut two days later, starting in a 1–3 away loss against defending champions Manchester City.
Granero scored his first goal for QPR on 6 October 2012, but in a 2–3 defeat at West Bromwich Albion.
On 15 August 2013, after his team's relegation, Granero was loaned to Real Sociedad in a season-long move. On 17 September, after entering the pitch in the 81st minute of an eventual 0–2 home loss against FC Shakhtar Donetsk for the campaign's UEFA Champions League, he suffered an anterior cruciate ligament injury to his right knee, being sidelined for approximately six months.
Following his loan at the club, Granero signed a long-term deal with Real Sociedad on 28 July 2014, for an undisclosed fee. He played his first game in his second spell on 24 August, starting in a 0–1 away loss to SD Eibar.
On 7 July 2017, Granero signed a three-year contract with Espanyol.
After having helped Spain to the 2006 UEFA European Under-19 Championship, Granero made his debut for the under-21s on 6 February 2007, in a friendly match against England (2–2). He appeared for the nation at the 2009 UEFA European Under-21 Championship, in an eventual group stage exit.As of 18 September 2017
Copa del Rey: Runner-up 2007–08
La Liga: 2011–12
Copa del Rey: 2010–11
Supercopa de España: 2012
UEFA European Under-19 Championship: 2006