Mullett was Concord's head football coach from 1989 to 1998. Under Mullett, the Mountain Lions won back-to-back WVIAC championships in 1989 and 1990, and qualified for the NAIA playoffs in 1992. He was WVIAC Coach of the Year in 1990.

Mullett helped six CU players earn All-American honors. His 51 coaching victories are second in Concord history and 15th all-time in the WVIAC.