BUFFALO — The Buffalo Sabres launched their offseason overhaul Friday by acquiring an additional first-round draft pick from the Philadelphia Flyers in exchange for defenseman Rasmus Ristailainen.

Eager to build its roster, Buffalo grabbed the Flyers’ first-round pick in the trade struck hours before the Sabres were scheduled to open the NHL draft with the top overall pick. The acquired pick was 13th in the draft order after the NHL stripped the Arizona Coyotes of their first-round pick, 11th overall, for testing players in violation of NHL combine policy.

Buffalo also got fifth-year defenseman Robert Hagg and a second-round pick in 2023 as part of the deal while Philadelphia gave a big, bruising boost to its blue line.

“We certainly look at Ristolainen as someone who can be a big part of our future going forward,” Flyers general manager Chuck Fletcher said after paying a considerable price to land the hard-hitting defenseman who has averaged nearly 24 minutes of ice time during his eight-year career.

“We like our defense core. We felt like we had good pieces. But we lacked size and physicality on the back end.”

Fletcher is betting the 6-foot-4, 218-pound Ristolainen improves in what should be a second-pairing role in a more structured system.

Ristolainen gives the Flyers another right-shot defenseman for their top four after acquiring Ryan Ellis from Nashville last weekend. Philadelphia also freed up cap space this week by trading defenseman Shayne Gostisbehere to Arizona.

The 26-year-old Ristolainen has one year remaining on a six-year, $32.4 million contract, which is being fully picked up by the Flyers.

For Buffalo, the trade could be the first of several made by general manager Kevyn Adams, who is also shopping captain Jack Eichel and forward Sam Reinhart.

Each of the three players raised questions about their futures in Buffalo in May after the Sabres finished last in the standings for the fourth time in eight years and extended their playoff drought to an NHL record-matching 10th season.

Ristolainen spilled his frustrations following the season by saying he informed Adams he was open to be traded. Two years ago, he expressed similar desires in questioning whether he was part of the problem in Buffalo.

Ristolainen is looking forward to a fresh start in Philadelphia, which missed the playoffs last season following a second-half collapse.

“We had really tough years in Buffalo. I played a big part. I was one of the leaders there and we couldn’t make the playoffs,” he said. “I’m very excited to go to Philadelphia. I’m going to do anything I can to make the playoffs and make a run there.”

Ristolainen had four goals and 18 points in 49 games with the Sabres last season. Overall, he has 46 goals and 245 points while averaging nearly 24 minutes per game in ice time in 542 career games. From Finland, he was selected by Buffalo in the first round of the 2013 draft.

Fletcher defended Ristolainen’s analytic numbers as being the result of playing in numerous systems — he played under six coaches in Buffalo — and an ever-changing set of defensive partners.

The Sabres are in flux yet again under new coach Don Granato, and focusing on rebuilding through youth.

Eichel, the face of the franchise, is on the trade block in part because of a dispute with the team over how to treat a herniated disk that forced him to miss the final two months of the season. Eichel revealed the rift in May by calling it “a disconnect” that has led him to question his future in Buffalo.

Eichel favors surgery while the team is against it because the procedure has never been performed on an NHL player.

Hagg, also 26, was in and out of the lineup last season as either the team’s sixth or seventh defenseman and finished with had two goals and 5 points in 34 games. Selected by Philadelphia in the second round of the 2013 draft, Hagg has 13 goals and 47 points 236 career games.