Dineen was then hired by the Phoenix Coyotes as an assistant coach for their AHL affiliate, the Springfield Falcons of the AHL, for the 2003–04 season. The next season, the Coyotes changed their AHL affiliation to Utah Grizzlies, which had since joined the AHL after the IHL dissolved, and Dineen was retained by the organization as an assistant coach under Pat Conacher in the 2004–05 season. The Grizzlies suspended operations in 2005 and Dineen was moved to the Coyotes' new AHL affiliate, the San Antonio Rampage in the same role from 2005 to 2007. The Coyotes released the entire Rampage coaching staff the end of the season.