He also coached the Washington Capitals from 2002 - 04 .
The 51 - year - old Cassidy was with the team 's AHL club in Providence for nine seasons before becoming an assistant with Boston this season .
Cassidy also coached the Washington Capitals from 2002 - 04 .
The 51 - year - old Cassidy was with the team 's AHL club in Providence for nine seasons before becoming an assistant with Boston this season .