SUNRISE, Fla. -- Boston Bruins general manager Don Sweeney made a big splash on Day 1 of the 2015 NHL draft with a major overhaul of the team's cap-strapped roster with his sights on a possible rebuild.

Sweeney traded veteran forward Milan Lucic to the Los Angeles Kings, and in a separate transaction the GM traded 22-year-old defenseman Dougie Hamilton to the Calgary Flames. As part of the moves, the Bruins acquired two first-round picks in this year's draft, giving them Nos. 13, 14 and 15.

With those picks, the Bruins selected defenseman Jakub Zboril, forward Jake DeBrusk and forward Zachary Senyshyn, respectively.

Despite the shake-up, Sweeney says he believes the Bruins will still contend for a playoff berth in the 2015-16 season.

Along with the Kings' first-round pick (No. 13), the Bruins acquired goaltender Martin Jones and prospect Colin Miller. The Bruins also retain $2.7 million of Lucic's contract. Along with the Flames' first-round pick (No. 15), Boston also acquired Calgary's 45th and 52nd overall selections.

Sweeney also announced he re-signed veteran defenseman Adam McQuaid to a four-year deal worth $11 million.

For a team that's built with a defense-first mentality, it's going to be difficult to fill the void left by Hamilton. The former first-round pick (No. 9 overall in 2011) has the size and skill to be a top defender for a long time.

Hamilton is a restricted free agent this summer and the sides had been talking about a long-term contract before Sweeney realized it wasn't going to work out.

"The offer that I offered was certainly in line with comparables," Sweeney said. "So, the spread for me was an indication that maybe we'd be better served if we went in a different direction at this time."

The Bruins were well aware that more than one team was planning to extend Hamilton an offer sheet. Sweeney said as talks came down the stretch, the Bruins felt they positioned themselves to sign Hamilton, especially given the fact the team was in the process of trading Lucic. The pending offer sheets from other teams did not scare Sweeney and they would have matched any offer.

"We extended Dougie a very significant contract offer and it didn't lead us to where we thought we'd be able to [have] him comfortable being part of our group long term," Sweeney said.

Lucic had just returned home to Vancouver after a family trip to Disneyland in Southern California when he learned of the trade. Over the past few days, he heard and read the rumors of a possible trade and described it as an emotional time.

"I'm anxious, sad and excited all at the same time," he said.

Sweeney said it was a difficult conversation to have because of all that Lucic meant to the Bruins' organization. Lucic has one year and $6.5 million remaining on his current contract and he was hoping for a contract extension sooner than later. Sweeney admitted the sides talked about that possibility, but the Bruins realized they didn't have the resources to give the pending unrestricted free agent what he was looking for.

"I can't tell you how difficult the call was to make, and I expressed that to Milan," Sweeney said. "It was a very difficult conversation to have. I just felt the situation we were in it was going to be very difficult to extend the offer to the level that it would take to retain Milan going forward."

When Lucic received the call he said he could sense it in Sweeney's voice.

"It was definitely an emotional call," Lucic said.

Bruins assistant captain Patrice Bergeron reacted to the changes the team made and said he understands it's part of the business.

"It's always sad to see players leave and it's the tough part of the business," Bergeron told ESPN.com. "I definitely wish them all the best in Calgary and L.A., respectively."

With all the changes the Bruins made in a 24-hour period, including the trades of Lucic, Hamilton and Carl Soderberg, Bergeron says he trusts Sweeney's vision.

"I've had a chance to play with Looch for the last eight years and I won a Cup with him. We are friends and I'll miss him. Dougie is a young player with a bright future ahead of him and I wish him all the best, also," Bergeron said. "That being said, it's the business we are in and we are aware when we sign in. I trust Don and the management's plan moving forward."

Before the 2006 draft, the Kings met with Lucic three times and the forward thought he would be chosen by Los Angeles with the No. 48 pick. Instead, he went to the Bruins at No. 50.

"What I thought was going to happen in 2006 has happened today," Lucic said.

He also says he believes the Bruins will be fine moving forward, especially with players like Tuukka Rask, Bergeron and David Krejci.

"I was part of that organization for a long time and I was fortunate to be part of the identity," Lucic said. "They'll be fine. I wish them all the best, but not against the Kings."

Lucic's size, strength and ability will add to an already solid Kings team that has won a pair of Stanley Cup in recent years.

"The most exciting part about moving on from Boston is going to a team that knows how to win," Lucic said. "I hope to help them win another Stanley Cup."

Sweeney and the Bruins have the assets now to possibly make other changes in the future. Jones, who will back up starter Rask, has the ability to become a No. 1 goaltender in the NHL. If Jones develops into what many believe he will, it could allow Sweeney to create more cap space by moving Rask, and his $7 million per season contract, in the future. Lucic was trending down and obviously wanted big money with his next contract, so that deal makes sense in the long term.

There's no doubt Sweeney and the Bruins have a long-term plan in mind and it began in earnest Friday.