Born in Esplugues de Llobregat, Barcelona, Catalonia, Ruiz arrived in RCD Espanyol's youth system in 2006 at the age of 17, from neighbouring UE Cornellà.

[5] Coach Mauricio Pochettino fielded him in a further 21 La Liga games that campaign, with the team finally finishing 11th; he added two goals, against Málaga CF (2–1 away defeat)[6] and Atlético Madrid (3–0, home).

[8] On 31 January 2011, he was sold to SSC Napoli for €6 million cash in a four-and-a-half-year contract, with the Italians also ceding the sporting rights to Jesús Dátolo who was playing with the Spaniards on loan.

[13] On 12 December 2013, Ruiz was sent off in a 1–1 home draw against FC Kuban Krasnodar in the group stage of the UEFA Europa League, for a professional foul on Djibril Cissé.

[16] Ruiz scored his first league goal for Villarreal on 7 April 2017, in a 3–1 home defeat of Athletic Bilbao where he also received his marching orders after a straight red card with 15 minutes left.