[2] Born in Sant Feliu de Guíxols, Girona, Catalonia, Crosas came through the ranks at La Liga club FC Barcelona and signed a five-year contract in 2006.

On 8 November 2006, Crosas made his first-team debut in a Copa del Rey tie against CF Badalona, coming on as a substitute for Andrés Iniesta in the 76th minute.

[3] On 11 January 2008, Barcelona and Ligue 1 club Lyon reached an agreement in which Crosas would play on loan for the French champions until the end of the season, because of the number of players competing for his central midfield position.

[4] Crosas made his Ligue 1 debut for Lyon on 20 January 2008 in a match against Lens, starting in place of Juninho, who was out with a dislocated toe.

[9] In the 2009–10 season, Crosas was not initially a regular starter in midfield as Massimo Donati and loan signing Landry N'Guémo were first picks.

After Donati's transfer to Bari, Crosas got a chance to shine and forged a successful partnership with N'Guemo, becoming a staple of the Celtic starting eleven.

[10] At the start of the 2010–11 season, Crosas fell out of favour under new Celtic manager Neil Lennon, but on 22 September he came off the bench to replace Joe Ledley in a 6–0 League Cup win over Inverness Caledonian Thistle.

[11] Crosas was transferred by Celtic to Russian Premier League side FC Volga in February 2011 for £300,000, signing a contract until December 2014.

After having trouble adapting to life in Russia with FC Volga,[13] Crosas signed a three-year deal with Mexican side Santos Laguna.

On 20 May 2012, he played the entire final match of Torneo Clausura 2011–12 against Rayados de Monterrey where Santos Laguna won the title after a 2–1 victory (3–2 in global).

[citation needed] After leaving Santos Laguna in 2014, Crosas played for U. de G. and Cruz Azul, serving subsequent loan stints at CD Tenerife[18] and Tampico Madero.