"He's been struggling with it, but it got worse the last few days, few games, to the point where in the Boston game I pulled him … I didn't play him in the third period because of where he was at pain-wise and he wasn't able to skate or push," Sabres coach Dan Bylsma said.
Ennis was limited to 23 games last season because of two concussions. The second came on Dec. 30, 2015, when he was checked by Washington Capitals captain Alex Ovechkin. Ennis missed the remainder of the season.
"It's disappointing for Tyler," Bylsma said. "This is a situation he's been dealing with for a little bit, the past little while, days, maybe a week. Kind of just extremely disappointing to get the news he's going to be out for a bit of time having surgery, which he had this morning. He's had a tough go of getting on the ice and playing games, which he's had the last nine months, 10 months."