He started his professional career with Barcelona, without much success, and went on to amass La Liga totals of 169 matches and eight goals in representation of six other clubs. He added 149 games and 25 goals in the Segunda División, over six seasons.
After two loans with interesting playing time, at Real Oviedo[2] and Racing de Santander, Carreras returned to Barça. Although he appeared regularly in 1995–96's league, they came out empty in silverware.
Carreras then lived his most steady period at RCD Mallorca,[3] although never an undisputed starter. He achieved top-flight promotion in his first season, totalling 128 competitive appearances during his spell in the Balearic Islands.
Subsequently, Carreras had similar experiences with both Atlético Madrid[4] and Deportivo Alavés.[5] after featuring regularly in both clubs' promotion from the Segunda División, he saw very little time the following campaigns; in between, he spent 2003–04 with Real Murcia also in the top division.
Carreras' career would end on a sour note: when playing for the Basque side, he clashed with eccentric owner/chairman/manager Dmitry Piterman.[6] Teammate Roberto Bonano, who stepped up in his defence, was also suspended;[7] both retired shortly afterwards.
On 30 May 2013, after avoiding relegation for the second time in a row, Carreras resigned amid rumors he could sign for a top team in the same league.[12] It finally happened on 26 February of the following year when he was appointed at the helm of RCD Mallorca, replacing the fired José Luis Oltra.[13]
Carreras was relieved of his duties on 20 May 2014, after winning only ten points out of 36.[14] On 27 December 2015 he was named Real Zaragoza manager[15] but, after failing to reach the play-off positions with a 6–2 loss at already relegated UE Llagostera in the last matchday of the season, he resigned.[16]
On 21 June 2017, Carreras signed a two-year contract with another second-division club, Gimnàstic de Tarragona.[17] After just four league games (one draw and three losses), he was dismissed.[18]
Carreras was hired by a foreign club for the first time in December 2018, when Japan's Sagan Tosu named him as manager for the upcoming season; they had recently secured the high-profile transfer of his former Atlético teammate Fernando Torres.[19] He resigned the following 5 May, with the side last-placed having scored just once in their first ten J1 League matches.[20]