Cassidy told reporters on Sunday before the Bruins faced the Tampa Bay Lightning in Game 5 that he met with Marchand after senior vice president of hockey operations Colin Campbell spoke to Marchand and Bruins general manager Don Sweeney on Saturday. Marchand was told to stop trying to lick opponents.
"I saw the directive from the league," Cassidy said. "I talked to Marchy about it [and said], 'That's what the league's asked for, and we need you on the ice. We need you playing.' So zip it, or whatever term you used."
Cassidy said he understands that Marchand was trying to agitate opponents but wants the winger to try another tactic.
"If part of his MO is to annoy people, find another way to do it," Cassidy said. "That's basically what's in front of him now. ... preferably by scoring some goals -- that would be the best way probably."
Marchand has been held without a goal since Game 1 against the Lightning. He has contributed four assists in the past three games, all losses, as the Bruins have fallen behind 3-1 in the series.
Marchand's antics continued Friday in Game 4, in which he hit Lightning forward Ryan Callahan with a low-bridge check in the second period. Callahan later shoved Marchand's face, and Marchand responded by sticking out his tongue and licking Callahan.
"Well, he punched me four times in the face, so you know, he just kept getting close," Marchand said regarding the incident.
In Game 1 of the Bruins' opening-round series against the Toronto Maple Leafs, Marchand licked the face of Leafs forward Leo Komarov after having previously kissed him on the cheek during a regular-season game.
The NHL said similar behavior from Marchand could result in supplemental discipline.