In an interview at the April 2011 Big Four concert, Robert Trujillo said Metallica will work with Rick Rubin again as producer for the new album and were "really excited to write some new music. There's no shortage of riffage in Metallica world right now." He added, "The first album with Rick was also the first album for me, so in a lot of ways, you're kind of testing the water. Now that we're comfortable with Rick and his incredible engineer, Greg Fidelman, who worked with Slayer, actually, on this last recordit's my heroit's a great team. And it's only gonna better; I really believe that. So I'm super-excited." In June 2011, Rubin said Metallica had begun writing its new album.