Before casting Keira Knightley as Gretta, Carney considered casting a pop singer such as Adele in the main role, as well as a number of other actresses including Scarlett Johansson, who was at one point attached to the project.[2][6] Knightley, who had never sung professionally before, prepared for the role by training with a vocal coach and learning how to play a guitar.[7] Mark Ruffalo was Carney's first choice for the role of Dan,[2] and agreed to star in the film after Carney sent him the first draft of the screenplay.[6] Singer Adam Levine was also the only person Carney considered casting as Dave, and won the role after talking with Carney over Skype and recording some dialogue as an audition;[8] he declined to be paid for appearing in the film.[9] Although he had had minor acting parts on television before, Begin Again marked his first role in a film.[8] Carney approached James Corden to appear in the film after admiring Corden's performance in the lead role in a Broadway production of One Man, Two Guvnor