He made a name for himself at Espanyol (with whom he won a Copa del Rey and reached the 2007 UEFA Cup final) and also played professionally in France, England, Greece, Turkey, Italy and Slovenia, notably spending three years with Galatasaray.

He made his first-team debut on 25 February 2001 under Luis Aragonés in La Liga, as a 71st-minute substitute for Lluís Carreras in a 2–1 loss at Racing de Santander,[3] and scored his first goal on 27 May by coming off the bench to conclude a 4–0 home win over Rayo Vallecano that secured a UEFA Champions League place.

In the 2002–03 campaign, already an undisputed starter, Riera helped the local team to the conquest of the Copa del Rey,[5] and scored four league goals in 35 games.

[7] He made 66 competitive appearances for the Ligue 1 side over a two-year spell, netting nine times;[8] this included five in a run to the quarter-finals of the UEFA Cup in his first season before elimination by eventual winners Valencia.

[14] In his first season he played only eight league matches, prompting a January 2006 loan move to Manchester City[15] where he was also unable to establish himself, scoring his only goal against Newcastle United in a 3–0 home win on 1 February.

During that season, Espanyol reached the final of the UEFA Cup at Hampden Park, Glasgow, where they played fellow Spaniards Sevilla; he scored to level the game at 1–1, but his team eventually lost 3–1 on penalties.

[30] Riera scored his first goal against Kerkyra in a 2–0 home win,[31][32] and appeared in 28 competitive matches during the season as the Piraeus team won the Super League Greece.

[34] He scored his first goal in the Süper Lig on 25 January 2012 in a 4–0 home defeat of Ankaragücü, and was an habitual first-choice in his first season as the Istanbul-based team won the national championship; he was also involved, however, in a punching session with teammate Felipe Melo just before the playoffs started.

[35] Following the arrival of prospect Nordin Amrabat for the 2012–13 campaign, Riera was reconverted by manager Fatih Terim into an attacking left-back, mainly due to the lack of options in the position other than injury-prone Hakan Balta.

[41] After the match, he was charged by The Football Association for improper conduct, having confronted the officials and having to be dragged away by his team-mates;[42] he was given a two-match ban although only one remained to end the campaign,[43] and he subsequently returned to Udinese.

[53] He joined the team also as an assistant sporting director, and made one brief appearance against Primorje in the first game of the second half of the season; he was then suspended from training and his contract was cancelled unilaterally in July 2016.

[57] Riera was again called to the squad in October 2008 for two 2010 FIFA World Cup qualifiers after Sevilla's Diego Capel withdrew with an injury,[58] and played 12 minutes in a 3–0 victory in Estonia.

[66] He made his debut three days later at home to Differdange 03 in the first qualifying round of the UEFA Europa Conference League, drawing 1–1,[67] and requiring extra time in the second leg to advance through the tie.

[78][79] A day after leaving Celje, Riera became the new manager of Bordeaux – now in Ligue 2 – returning to the club 18 years after his playing tenure and signing a contract until June 2025.