Bruins coach Claude Julien said after Friday's practice that Nathan Horton did not react well to skating earlier this week, and is "back to square one" in his recovery from his latest concussion.
"He's been pulled back," Julien said. "He's got some symptoms, so we pulled him back. That's why I said as far as for me to come out every and [say there's a] step forward, a step backward. He's back to square one and we're giving him some time here. Those symptoms, once he got back on the ice, came back."
Horton rode the stationary bike late last week and took to the ice on Sunday, but when symptoms returned, the team pulled the first-line winger back.
Horton suffered his second concussion since June on a hit from Philadelphia's Tom Sestito on Jan. 22. His concussion has kept him out of the last six games.
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