For those in the organization, it was the suddenness of it happening that affected them most.
"This was a situation I think everyone knew was going to take place, it's just the timing of it was a bit quicker than people would've thought," Sabres coach Ron Rolston said. "Obviously losing a player that has meant so much to the organization over the years is tough. He's put a lot of his career, his sacrifices, dedication to the Buffalo Sabres."
Vanek spent the first eight seasons of his career in Buffalo before being dealt Monday night.
"It's completely shocking in the essence of a guy that's been around for a long time here and he's been very successful in Buffalo," Sabres captain Steve Ott said. "In the same instance, it's part of the business. He's an unrestricted free agent at the end of the year. There's been rumblings and rumors of what's gone on here. I mean, we got back a heck of a player."
Moulson is a three-time 30-goal scorer and, like Vanek, is also in the final year of his contract. He went from being an unsigned ninth-round pick by the Pittsburgh Penguins to a forgotten man for the Los Angeles Kings to one of the best low-risk signings in recent seasons with the Islanders.
He formed a strong partnership with center John Tavares and averaged 0.38 goals per game in the past four seasons with New York. That was tied for 21st in the League during that span, and just behind Vanek's 0.4 goals per contest.
Moulson is expected to skate on the top line Monday night for the Sabres in Vanek's old spot next to Cody Hodgson.
"I'm sure I'll be around the net as usual," Moulson told reporters. "I don't venture too far from there."
Vanek was part of a small core of players in Buffalo that were veteran leaders. He along with goalie Ryan Miller, forward Drew Stafford, and defenseman Henrik Tallinder had spent the better part of their careers together as Sabres.
"It's sad, but that's the way things are going now," Stafford said. "At the same time it's a business. It's the unfortunate side of things. You lose great friends and great teammates. At the same time, we have to find a way to move forward and we've got to focus on trying to get some wins here."
"I think it was bound to happen sooner or later. It happened sooner," Tallinder said. "Yeah, they got some draft picks, I mean that's good for the future I guess. Drafting is always kind of a lottery anyway, but I think we got a good player here and we lost one. It's for the future and that's why we did it."
For some of the younger players, Vanek's departure hits home a little harder.
"He's definitely a tough guy to lose," defenseman Tyler Myers said. "But I think most of the guys in the room here were expecting something might happen this year. The fact that it's become a reality is still settling in. I wish [Vanek] all the best. He was a huge help for me coming into this organization."
Should Vanek still be a member of the Islanders by the end of the season, he would make his return to Buffalo on April 13, 2014, the Sabres' final game of the season.
“It’s hard to watch all of them go,” Miller said. “It’s no different each time. All these guys have been close friends and great hockey players.”