Sweeney made two key trades for the Bruins prior to the deadline, landing Marcus Johansson from the New Jersey Devils for a pair of draft picks and acquiring Charlie Coyle from the Minnesota Wild in exchange for Ryan Donato and a conditional draft pick.
The Bruins GM didn't make any major offseason splashes, but the low-risk depth signings of Jaroslav Halak, John Moore, Joakim Nordstrom, and Chris Wagner proved integral to Boston posting the second-best regular-season record in the Eastern Conference.
Armstong endured one of the busiest offseasons in Blues franchise history. He landed Selke Trophy candidate Ryan O'Reilly from the Buffalo Sabres without giving up any major assets and signed Tyler Bozak, David Perron, and Patrick Maroon in free agency.
His best move, though, may have been not making one at all. After an abysmal start to the season, the Blues were rumored to be sellers, but Armstrong gave his group time to gel before making any major moves. The team rewarded him with one of the league's hottest second-half runs, going from last in the NHL on Jan. 2 to a playoff berth by the end of the regular season.
Waddell had a busy offseason of his own during his first summer at the helm in Carolina. He made a blockbuster trade with the Calgary Flames at the draft, shipping out highly touted youngsters Elias Lindholm and Noah Hanifin to acquire Dougie Hamilton and Micheal Ferland.
He also solved the club's longstanding goaltending issues by signing Petr Mrazek to a one-year deal and claiming Curtis McElhinney off waivers from the Toronto Maple Leafs. His pre-deadline trade sending Victor Rask to the Minnesota Wild in exchange for Nino Niederreiter has proven to be one-sided in Carolina's favor.
The NHL's 31 general managers vote on the award at the end of the regular season. The winner will be announced on June 19.