Juan Ruax encouraged Carreras to audition for what was to become his first tenor role at the Liceu, Flavio in Norma, which opened on 8 January 1970. Although only a minor role, the few phrases he sang caught the attention of the production’s leading lady, the eminent soprano and fellow Catalan, Montserrat Caballé. She asked him to sing Gennaro with her in Donizetti’s Lucrezia Borgia, which opened on 19 December 1970. It was his first principal adult role, and the one which he considers to be his true debut as a tenor. In 1971, he made his international debut in a concert performance of Maria Stuarda in London’s Royal Festival Hall, again with Caballé singing the title role. Caballé was instrumental in promoting and encouraging his career for many years, appearing in over 15 different operas with him, while her brother and manager, Carlos Caballé, was also Carreras’s manager until the mid-1990s.
During the 1970s Carreras’s career progressed rapidly. In late 1971, he won first prize in Parma’s prestigious Voci Verdiane competition which led to his Italian debut as Rodolfo in La bohème at the Teatro Regio di Parma on 12 January 1972. Later that year he made his American debut as Pinkerton in Madama Butterfly with the New York City Opera. Other major house debuts followed – the San Francisco Opera in 1973, as Rodolfo; the Philadelphia Lyric Opera Company in 1973, as Alfredo in La traviata; the Vienna Staatsoper in 1974, as the Duke of Mantua in Rigoletto; London’s Royal Opera House in 1974, as Alfredo; the New York Metropolitan Opera in 1974, as Cavaradossi in Tosca; and La Scala, Milan in 1975, as Riccardo in Un ballo in maschera. By the age of 28, he had already sung the tenor lead in 24 different operas in both Europe and North America, and had an exclusive recording contract with Philips, which resulted in valuable recordings of several less often performed Verdi operas, notably Il Corsaro, I due Foscari, La battaglia di Legnano, Un giorno di regno, and Stiffelio.
Carreras’s leading ladies during the 1970s and 1980s included some of the most famous sopranos and mezzo-sopranos of the day: Montserrat Caballé, Birgit Nilsson, Viorica Cortez, Renata Scotto, Ileana Cotrubas, Sylvia Sass, Teresa Stratas, Dame Kiri Te Kanawa, Frederica von Stade, Agnes Baltsa, Teresa Berganza, and Katia Ricciarelli. His artistic partnership with Ricciarelli began when they both sang in the 1972 La bohème at Parma and lasted for 13 years, both in the recording studio and on stage. They later made a studio recording of La bohème for Philips Classics and can be heard together on over 12 other commercial recordings of both operas and recitals, predominantly on the Philips and Deutsche Grammophon labels.
Of the many conductors he worked with during this period, the one with whom Carreras had the closest artistic relationship and who had the most profound influence on his career was Herbert von Karajan. He first sang under Karajan in the Verdi Requiem at Salzburg on 10 April 1976, with their final collaboration in a 1986 production of Carmen, again at Salzburg. With Karajan’s encouragement, he increasingly moved towards singing heavier lirico-spinto roles, including Aïda, Don Carlos, and Carmen, which some critics have said were too heavy for his natural voice and may have shortened his vocal prime.