A front-rower, Cusack was one of the last remaining top-level league players to hold a job outside football, working part-time as a plumber.

Cusack was awarded the 2002 Sydney Roosters season's Clubman of the Year and played in their 2002 NRL Grand Final victory over the New Zealand Warriors.

He was also a member of the Roosters side that won the 2003 World Club Challenge, and appeared in the 2003 NRL Grand Final loss to the Penrith Panthers.

Cusack played for the Roosters from the interchange bench in their 2004 NRL grand final loss to cross-Sydney rivals, Canterbury-Bankstown.

[2] In 2005, Cusack joined the South Sydney Rabbitohs, that year winning the George Piggins Medal as the club's best and fairest player for the season.