Mike Longabardi has signed with the Suns to join their staff as an assistant coach.

Longabardi, 40, has spent six seasons as an assistant coach with Boston under Doc Rivers after also spending two years as an assistant coach for Jeff Van Gundy in Houston, where he broke into the NBA as a video coordinator.

Longabardi’s hire completes the core of new Suns head coach Jeff Hornacek’s staff with assistants Jerry Sichting, Kenny Gattison and Mark West already on the job.

Longabardi had been charged with being the Celtics’ defensive coordinator for the past two seasons, following Lawrence Frank and Tom Thibodeau in that role. The Celtics finished seventh in defensive field goal percentage last season and first in 2011-12 at 41.9 percent.

Of his eight seasons, he was a part of seven playoff staffs, including the Celtics’ 2008 championship team and the 2010 NBA Finals team.

Previous to his first NBA job with Houston in 2003, Longabardi served as a college assistant coach at Pfeiffer, Adelphi, Lafayette and Towson State.