BOSTON — Don Sweeney opened his press conference by expressing regrets that the Bruins had to fire Coach Jim Montgomery, but thought the move was necessary to stop the team’s season-long slide.

The general manager explained why the team made the move and what he expected going forward.

“It came from our team not performing to our level of expectations that we have grown to appreciate. For me, I just had to change course. That has not generally been my nature,” said Sweeney, who added that he and Montgomery were in extension talks before the season. “We want to figure out what this team is capable of. We have 60 games to go. That’s a lot of season. But you can’t stay in neutral.”

Sweeney said it started in training camp when injuries and other absences slowed progress.

“I felt our camp was just a flat line across the board,” he said. “That was the first troubling sign. Whether they thought it was going to be easy and the guys that were really good last year thought it was going to just fall into place. This league is really humbling and it will expose you in a hurry. You have to have more structure in place to fall back on success.”

Sweeney said the lack of fight and consistency was widespread on the roster.

“It’s hard to wrap your head around the fact that you’ve got upwards of 10 players off of what their norms would be. That’s concerning,” he said. “Specialty teams, which have been a strong point of our organization, are well underwater. … I didn’t like the direction. We had a small incremental bump in terms of starting to play the right way, but we couldn’t maintain it.

“Those are the things that bother me as a general manager. Our team can’t stay as close as they’ve been and can’t get through the adversity piece within a game. That why I made a decision at this point. This group is capable of more and that’s what we’re going to expect from them.”

The Bruins named Joe Sacco as the interim coach and will give him a chance to prove himself worthy of the job permanently. He said Sacco, a fomer Avalanche head coach, was the only candidate when Montgomery was dismissed.

“We’ve put Joe in a position to get his hands on the steering wheel. Joe is well equipped to be able to do this. He’s had institutional knowledge for a number of years with teams that have been successful and where it needs to get back to be successful,” said Sweeney, who thought his players would experience the natural lift that comes with new coach. “You hope you’re going to get a bounce of some kind. I certainly expect it. I know what the pride level of our players is. I would expect them to take ownership and improve.”

If they don’t, he said more changes will follow.

“Moving forward, it rests with me now. The players have to understand that they’re not where they need to be,” he said. “We’re either going to get back there or there’s going to be continued changes across the board.”