Assistant Alain Nasreddine was named as his replacement and coached New Jersey in a 4-3 loss to the Vegas Golden Knights at Prudential Center.
"Lot of emotions, lot of mixed emotions," the 44-year-old said prior to the game. "I just found out a couple of hours ago, so a lot goes through your mind. I can't help but think about John and the relationship we've had the last 10 years, and those are not great circumstances. It is an opportunity, but you know it's [going to] take time to settle in, but we have a game to win tonight, so that's where the focus is right now."
Hynes was 150-159-45 in five seasons with the Devils and was the fifth longest-tenured coach in the NHL since he was hired June 2, 2015. He signed a new multiyear contract with New Jersey on Jan 3.
"John [did] a really good job here over the past four-plus seasons in terms of establishing the way things [are] both on and off the ice, but everybody had higher expectations," Devils general manager Ray Shero said. "But ... it's collectively as a group and our team. I don't think there's any one player that is performing, even at the level, let alone above, that we expect or maybe they expect. And that's a thing that's disappointing.
"Obviously change brings opportunity, not only for Nasreddine but also for our players, and there's opportunity for them to find out kind of where we are here and where we're going to go."
New Jersey (9-14-4) is 15th in the Eastern Conference and 30th in the NHL standings.
"You never want to see that (firing) happen," Devils captain Andy Greene said. "Obviously when there's a change in coach it's not because you're in a great place. He's a great coach and great person and he had to be sacrificed because of us in here because of the way we've been playing."
Devils forward Taylor Hall, who can become an unrestricted free agent after this season and has been the subject of trade rumors, would not say if he thought a coaching change was needed.
"That's not for me to answer, and really when I say I was genuinely shocked today, I was genuinely very, very surprised," he said. "I don't say that in a good or a bad way. As a player, that's not something you have literally any control over. We didn't play well enough as a team and we have a different head coach because of that. There's not one guy in here that's having a great year, having a year that they can look back in 10 years and say, 'Man, I played great that year.' As players we need to find that. We need to find a level that we all haven't shown this year. If [Alain] is the guy that can bring us to do that, then so be it."
New Jersey lost to the New York Rangers 4-0 on Saturday and to the Buffalo Sabres 7-1 on Monday.
"Obviously the [Rangers] game was not good, and the Buffalo game as a matter of trying to describe it," Shero said. "Those are the two, obviously the Buffalo game in particular, but the [Rangers] game was disconcerting as well, but the Buffalo (game) ... not even sure how to explain that one."
Shero addressed not letting Hynes coach Tuesday.
"I don't know that [that] would have done anything," Shero said. "I just thought that after the last couple games, last night in particular, it wasn't fair to him, it wasn't fair to us. I knew what I was going to do. [I made my] recommendation to [Devils owners] Josh Harris and David Blitzer, and so I think that was the timing, and to deal with, you know, today and not tomorrow, and there's no way I wouldn't be fair to John. And so it was time to time to do something."
The Devils qualified for the Stanley Cup Playoffs once under Hynes, losing to the Tampa Bay Lightning in five games in the Eastern Conference First Round in 2018.
New Jersey finished 27th or worse in the standings in two of the past three seasons and won the NHL Draft Lottery twice, selecting center Nico Hischier No. 1 in 2017 and center Jack Hughes No. 1 in 2019.
"[John] brought me to where I am right now with my game," Hischier said. "He taught me a lot, especially my first year, he gave me a lot of confidence playing me with [Taylor] and gave me a lot of good minutes, and I'm not taking that for granted, and it's been a pleasure working with him and I took a lot of good things."
Video: Devils relieve John Hynes of head coaching duties
Hynes is the third NHL coach to be replaced this season (Mike Babcock, Toronto Maple Leafs; Bill Peters, Calgary Flames).
"It can [make a difference], but it's not like a light switch, it just doesn't happen," Greene said. "A new voice is there, but you can't change the way we play in here; that's on us and that's what guys have to understand. Just because that happened doesn't mean everything is going to be perfect now and easier. We have to show some resiliency here, stick together and start to play the way we are capable of."
New Jersey led 2-1 Tuesday before Jonathan Marchessault scored a third-period hat trick for Vegas.
"The decision was made in the afternoon and you come up and you're coming in to try to prepare for a game and that's obviously a pretty big change, but I think it's something that we just had to dust ourselves off and we had a tough team coming in here tonight, and after the way last night's game went we wanted to obviously rebound from that, so I think we'll have some time here over the next couple of days to reflect and see what the magnitude of it is, but it is a fresh start," Devils forward Kyle Palmieri said.
Hynes is second in games coached (354) and wins in Devils history, trailing Jacques Lemaire (509 games, 276 wins) in each.
"I think best way to look at it, this may be the fresh start for everybody," Nasreddine said. "Like I said, this just happened. I mean, we're going to meet with some players. Everyone in that room has been underachieving, so there's going to be opportunities. You have to earn your opportunity and that's not going to change. I think it's like that for every team in every sport, so that's the bottom line, and the type of coach I am ... it's the same way. I've earned everything in life and I expect players to do the same thing with their job and how they play, so, yes, there will be opportunities, but at the same time everyone's going to have to earn those opportunities."
Nasreddine was an assistant coach with Wilkes-Barre Scranton in the American Hockey League for five seasons prior to joining the Devils staff in 2015. A sixth-round selection (No. 135) by the Florida Panthers in the 1993 NHL Draft, the defenseman had five points (one goal, four assists) in 74 NHL games in five seasons with the Chicago Blackhawks, Montreal Canadiens, New York Islanders and Pittsburgh Penguins from 1998-2008.
"Everything has been weird," Nasreddine said. "I'm an honest guy, I'll tell you how it is and what's been going through my mind. A lot of people would be excited about this, but like I said earlier when I first told you guys, it's mixed emotions. I owe this guy a lot, pretty much everything in my coaching career, so I get my opportunity, he loses his, so it's a little bittersweet."
Peter Horachek, who had been a pro scout for New Jersey, will be an assistant under Nasreddine. Shero said the coaching search will be wide-ranging.
"It's no different ... I usually have a list anyway for, whether it's assistant coaches and close to the minors or scouts or trainers," he said.
NHL.com staff writer Mike G. Morreale and senior writer Dan Rosen contributed to this report