The incident occurred in the first overtime during a Boston offensive zone set. Horton was battling for positioning in front of the net before visibly experiencing pain and skating off the ice. The situation appeared innocuous in nature, which has made the injury a bit mysterious.
Head coach Claude Julien was unable to update Horton's status during his post-game media availability because the team's doctors were still evaluating the extent of the injury.
"Nothing right now because there's nothing to say because our doctors haven't finalized the evaluation properly," he said.
The loss of Horton would be a significant blow to the Bruins. Skating on the top-line with David Krejci and Milan Lucic, Horton has registered 18 points (seven goals, 11 assists) in 17 postseason games. With Gregory Campbell already out of the lineup for the remainder of the year, the Bruins could be forced to dress another scratch in the event Horton is unable to play in Saturday night's Game 2.
Tyler Seguin replaced Horton with Krejci and Lucic during the overtime periods.