The play occurred behind the Lightning goal, Garrison appearing to get his left leg rolled up from behind by a Bruin. Garrison had to be helped off the ice by Anton Stralman and Brayden Point and headed back to the Bolts' locker room.
The team announced during the second intermission that Garrison sustained a lower-body injury. He did not return.
"It didn't look too good," Lightning head coach Jon Cooper said after the game.
"He couldn't put any weight on his leg. We'll have to see (Friday)."
Garrison has tallied one goal and eight assists in 67 games for the Lightning. The 32-year-old defenseman ranks third on Tampa Bay for blocked shots (86), fourth for average even-strength time on ice (16:29) and has missed just four games this season.
The Lightning are also missing forwards Tyler Johnson and Cedric Paquette, who each suffered a lower-body injury March 9 versus Minnesota and have missed the last seven games, including tonight's in Boston.
