The following year, following the appointment of Quique Sánchez Flores as new club manager, Domínguez became a mainstay in the Atlético Madrid team at left back where he displaced captain Antonio López from the starting XI.

[8] He ultimately made 46 appearances for the season across all competitions and was part of the squads which ended as runners-up in the Copa del Rey and as champions in the UEFA Europa League, where he started in a 2–1 win over Fulham.

[9][10] Domínguez continued to be a fixture in the Atlético Madrid first-team the following season and in August 2010 he started and played the full 90 minutes in the team's UEFA Super Cup win over Inter Milan.

He enjoyed success in the Europa League, however, coming on as a late substitute for Arda Turan as Atlético Madrid beat fellow Spaniards Athletic Bilbao 3–0 in the final to reclaim their title.

[16] On 27 June 2012, Bundesliga club Borussia Mönchengladbach completed the signing of Domínguez on a five-year contract for a fee of €8 million, bringing him in to replace the outgoing Dante.

[25][24] He revealed that he had been living with a back condition for the past few years and that, despite having twice undergone surgery in an attempt to rectify the problem, had been obliged to play by Gladbach.

[26] Domínguez later admitted to Spanish news publication Marca that he was considering taking legal action against Gladbach for medical negligence, claiming that the club had failed to treat his condition appropriately.

He started in all of Spain's matches, partnering Sporting de Gijón's Alberto Botía in central defense, as the national team won the tournament in Denmark.

[32] On 25 August 2011, following the UEFA European Under-21 Championship, Domínguez was called up to the senior national team by coach Vicente del Bosque for matches against Chile and Liechtenstein.

[33] Domínguez failed to feature in either match but made his debut on 26 May the following year, playing 45 minutes in a 2–0 friendly win over Serbia ahead of the 2012 European Championship.

[36] Though an Atlético Madrid supporter from birth, Domínguez revealed in a 2010 interview with The Guardian that he is fan of Premier League team Chelsea, and that the club's captain John Terry was his idol.