The team did not say whether Cassidy tested positive or not, so it's not yet clear how much time he will miss.
The 56-year-old Cassidy is in his sixth season coaching the Bruins. He took them to the 2018-19 Stanley Cup Final, where they lost to the St. Louis Blues. This season, the Bruins are 11-7-0 and fifth in the Atlantic Division.
The Bruins organization isn't just at a loss for the head coach. General manager Don Sweeney said the team is unable to call up players from the AHL's Providence Bruins because of a COVID-19 outbreak on the team.