Terms were not disclosed, but multiple media outlets reported it's for five years and $23 million.
"It certainly wasn't straightforward," Sabres general manager Tim Murray said Friday. "The day we signed him we were calling back and forth every 10 minutes. And then we got to a point where we thought, both sides moved, but we got to a point where we thought our last offer was very credible and in line with a lot of players of his caliber in the League."
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Ennis led the Sabres last season with a career-high 21 goals and was second in scoring with 43 points, but Murray wasn't yet ready to proclaim him the No. 1 center on a rebuilding team full of young talent.
"I don't know if I can pigeonhole him as that," Murray said. "He's a part of the team. Is he a center? Is he a winger? We talked about that with his agent, where he fits. He fits somewhere on this team. I have to look down the road, when I feel we're going to be a competitive team. And is he the No. 1 center on that team? He may not be. He may be this year, and next year he may be a No. 2 left winger. It depends on what we bring in here. It depends on how we surround him. That's going to dictate how he fits."
Murray did express satisfaction with the way Ennis performed last season under often trying circumstances.
"He had 21 goals on a not very good team, playing as the No. 1 center, getting the bad matchups," Murray said. "I thought considering his slow start -- I wasn't here for that, but I keep being told about it -- that he had a pretty successful year individually. And I think hopefully that translates into having a better year with better players around him."
The 26th pick in the 2008 NHL Draft, Ennis had 20 goals and a career-high 49 points as a rookie in 2010-11. He has 69 goals and 166 points in 267 regular-season games, and three goals and eight points in 13 Stanley Cup Playoff games.