Niagara Gazette — Buffalo has had two first-round picks in each of the past two drafts.
Veteran goalie Ryan Miller also is in the final year of his contract and is another candidate to be traded. Vanek has served as a co-captain this season, wearing the 'C' for home games.
"Like a lot of players he was shocked," Regier said about Vanek. "He was very professional. I thanked him. He was as good as he could be.
"It was a deal that was worked on and off for a while. It was something we felt we had to do."
Regier said he hasn't had recent trade talks regarding other potential free agents.
"Ryan continues to play extremely well," he said. "I probably talk to a third of the league of my counterparts on a weekly basis. You end up talking about a lot of things, and I'd leave it at that."
The Islanders also are in a rebuilding process as they look to improve on last season when they reached the playoffs and provided a challenge to the Pittsburgh Penguins in a six-game, first-round series.
New York has been up and down early this season, going 4-4-3 in its first 11 games, including 2-2-3 at home.
While the Islanders are losing a fan favorite and key linemate for captain John Tavares in Moulson, they are adding another proven star and goal scorer to play with Tavares.
Moulson has led the Islanders in goals in three of the past four seasons.
"Would like to thank all the great people and fans I was able to meet in NY," Moulson tweeted. "I will miss you all. This is the beginning of a new chapter."
Vanek has scored 40 goals twice and was an All-Star in 2009.
Vanek led Buffalo in power-play goals in seven of his nine NHL seasons and topped the league with 20 in the 2008-09.