When an NHL team acquires a player via the trade market, it's with the hope that the player will improve the roster.

Sometimes those moves can pan out, even succeeding beyond their wildest dreams.

A recent notable example is the Florida Panthers acquiring and signing power forward Matthew Tkachuk from the Calgary Flames on July 22, 2022. He led the Panthers to the 2023 Stanley Cup Final and was a key part of their 2024 Cup run this spring.

Sometimes, however, a significant move fails to pan out as hoped. The player could struggle to adjust to this new club. He could also have a year on his contract and prefer playing elsewhere when it expires.

A major trade can sometimes have consequences that haunt a general manager. He could trade away a quality player for a return that doesn't meet expectations. He could also make a move that ends up costing him his job.

Here's our look at the most regrettable trades from 2021-22 to 2023-24. Feel free to express your views on our picks in the app comments below.

Vegas Golden Knights Trade Evgenii Dadonov to Anaheim Ducks

The Vegas Golden Knights' attempt to move Evgenii Dadonov to the Anaheim Ducks before the 2022 NHL trade deadline would end up costing the Ottawa Senators dearly.

This story begins with the Senators trading Dadonov to the Golden Knights in July 2021 for defenseman Nick Holden and a 2022 third-round pick. However, they failed to disclose to the Golden Knights that Dadonov's 10-team, no-trade list was still in effect.

Fast forward to March 2022 when the Golden Knights shipped Dadonov to the Ducks in order to gain some salary-cap flexibility to reactivate sidelined winger Mark Stone and defenseman Alec Martinez as they battled for a playoff berth. On March 23, however, the league invalidated the trade because it didn't comply with the forward's no-trade clause.

Last fall, the NHL launched an investigation into Ottawa's role in the botched trade. On Nov. 1, 2023, the league announced the Senators would forfeit a first-round pick in one of the 2024, 2025 or 2026 drafts. This was because Sens general manager Pierre Dorion gave the Golden Knights the wrong information about Dadonov's no-trade clause.

The same day, the Senators announced they had parted ways with Dorion, who had held the GM job since April 2016.

The Dadonov trade started out as the Golden Knights' attempt to make a cost-cutting move. It ended up becoming a deal that had significant consequences for the winger's former club.

Alex DeBrincat to the Ottawa Senators

Approaching the 2021-22 season, then-Ottawa Senators general manager Pierre Dorion stated his team's rebuild process was over. He believed his club was ready for the next step when they would start to win and push toward playoff contention.

That step failed to materialize, as the Senators finished with the seventh-worst record in the league in '21-'22. That prompted Dorion to make a bold move entering the first round of the 2022 NHL Draft. On July 7, 2022, he shipped three draft picks (including the seventh-overall pick) to Chicago for winger Alex DeBrincat.

Then 24, DeBrincat was a two-time 41-goal scorer and a year away from restricted free-agent status with arbitration rights. However, Chicago GM Kyle Davidson was in the middle of a major roster rebuild and lacked first-round picks in the 2022 draft. DeBrincat was the only player who could fetch a return containing a first-rounder high in the selection order.

Dorion was confident he'd get DeBrincat signed to a long-term extension. A year later, however, the winger informed Senators management he wasn't interested, forcing Dorion to trade him to the Detroit Red Wings for winger Dominik Kubalik, prospect defenseman Donovan Sebrango, a conditional 2024 first-rounder, and a 2024 fourth-rounder.

DeBrincat had 66 points in 82 games during his sole season in Ottawa but the Senators still failed to improve. Dorion gave up a high-quality first-rounder as part of the return to land him and was forced to accept a lesser return to send him to Detroit.

Failing to ensure DeBrincat would sign with the Senators before acquiring him from Chicago was a big blunder on Dorion's part. He ultimately made a series of moves that did nothing to improve his club over the next two seasons.

New York Rangers Ship Pavel Buchnevich to the St. Louis Blues

On May 5, 2021, the New York Rangers promoted Chris Drury to team president and general manager. Among his first moves as GM was shipping Pavel Buchnevich to the St. Louis Blues for forward Sammy Blais and a 2022 second-round draft pick.

Buchnevich, then 26, was coming off a breakout performance during the COVID-shortened 2020-21 season. The right winger tallied a then-career high of 20 goals and 48 points in just 54 games skating alongside left wing Chris Kreider and center Mika Zibanejad.

The Rangers acquired Blais to add size and physicality to their checking lines, but he would last less than two seasons in New York before getting traded back to St. Louis. They would trade away the second-rounder from the Blues to the Winnipeg Jets on March 21, 2022, as part of the return in the Andrew Copp deal.

Writing about the Buchnevich trade a year later, The Athletic's Arthur Staple explained it was done to make room for young forwards Kaapo Kakko, Vitali Kravtsov and Alexis Lafrenière. However, Kakko has struggled to meet expectations while Kravtsov now skates in the KHL. Lafrenière has emerged as a scorer after struggling to adjust to playing his off-wing.

Buchenevich blossomed into a star with the Blues. He reached a new career-high of 30 goals and 46 assists for 76 points in 2021-22 and followed up with 67 points in 63 games in 2022-23 and 63 points last season. On July 2, 2024, he signed a six-year, $48 million contract extension.

The Rangers, meanwhile, struggled to find a suitable replacement. Patrick Kane, Vladimir Tarasenko, and Frank Vatrano have come and gone while Kakko is the ongoing subject of trade speculation. Their depth at right became a contributing factor in their difficulty getting past the Eastern Conference Final in 2022 and 2024.

Drury has made several trades since shipping Buchnevich to the Blues. That move could be his biggest regret as Rangers GM.

Los Angeles Kings Land Pierre-Luc Dubois From the Winnipeg Jets

The Los Angeles Kings finished 2022-23 with 47 wins and 104 points, marking the second-best regular-season performance in franchise history. However, they were eliminated from the first round of the playoffs by the Edmonton Oilers for the second straight season.

Kings general manager Rob Blake made a major move to bolster his depth at center. On June 27, 2023, he acquired Pierre-Luc Dubois from the Winnipeg Jets in exchange for forwards Alex Iafallo, Gabriel Vilardi, Rasmus Kupari, and a 2024 second-round pick. Dubois also signed an eight-year contract with an average annual value of $8.5 million.

Blake praised Dubois as "an elite two-way center with a unique skillset," citing his ability to "contribute to all facets of the game." He added how excited the organization was to have Dubois join the club and commit to a long-term deal.

Nearly a year later, Blake and the Kings were no longer excited about Dubois. On June 19, they shipped him to the Washington Capitals for goaltender Darcy Kuemper. Meanwhile, Iafallo, Vilardi and Kupari helped the Jets finished last season with the second-best regular-season record (52 wins, 110 points) in franchise history.

Dubois was a disappointment in Los Angeles, managing only 40 points in 82 games after back-to-back seasons of 60 or more points with the Jets. He saw mostly third-line center duty and even spent some time on their fourth line. The 6'4", 225-pounder managed just one goal in five playoff games as the Oilers again eliminated the Kings from the first round.

Blake took the blame for Dubois' struggles, saying he didn't do a good enough job integrating him into the right roles on the team. He managed to shed the big center's hefty contract shipping him to Washington for Kuemper, who has three years left on his deal with an AAV of $5.3 million but also struggled during his two seasons with the Capitals.

This move was among several this offseason that raised questions about Blake's management of the Kings. Already on the hot seat entering this season, he could risk losing his job if they fail to improve.

Erik Karlsson to the Pittsburgh Penguins

On June 1, 2023, the Pittsburgh Penguins hired former Toronto Maple Leafs general manager Kyle Dubas as president of hockey operations. Two months later, he also took over the role of Penguins GM.

It was apparent from the start that Dubas was trying to bolster the roster depth around aging stars Sidney Crosby, Evgeni Malkin and Kris Letang to give them one last shot at a championship run. He acquired winger Reilly Smith from the Vegas Golden Knights and added checking-line forwards Lars Eller and Noel Acciari.

Dubas then made the biggest splash of the 2023 offseason, acquiring Erik Karlsson on Aug. 6 from the San Jose Sharks in a multi-player deal involving the Montreal Canadiens. Karlsson, then 33, was coming off a career-best 101-point performance with the lowly Sharks, earning the James Norris Memorial Trophy for the third time in his career.

Pittsburgh also took on $10 million of Karlsson's $11.5 million average annual value through 2026-27. Still, with one of the league's best puck-moving defensemen on their blue line, the Penguins seemed poised to rebound from missing the playoffs in 2023, which ended a postseason streak that began in 2007.

Instead, the Penguins failed to qualify for the second straight season. Karlsson wasn't expected to have another season close to his 2022-23 stats, but his production dropped to 56 points in 82 games. Respectable for most offensive rearguards but not what was expected for a player joining what was supposed to be a playoff contender.

Dubas has spent this offseason adding younger players to his roster like Cody Glass, Blake Lizotte and Anthony Beauvillier, and restocking his prospect pipeline. Meanwhile, Karlsson's hefty cap hit limits attempts to add significant talent to the Penguins roster and likely led to Dubas trading pending free agent winger Jake Guentzel to Carolina in March.

Karlsson might bounce back this season after a year of adjusting to a new city and team. However, he's approaching the stage of his career when performance declines. Adding him to a roster already loaded with aging, expensive stars could become increasingly burdensome for the Penguins over the remaining years of his contract.

Chicago Blackhawks Acquire Seth Jones From the Columbus Blue Jackets

A three-time Stanley Cup champion between 2009-10 and 2014-15, Chicago's championship window was closing by the summer of 2021. Since 2015-16, they'd reached the playoffs three times and were eliminated from the opening round in each series.

Stars like Patrick Kane and Jonathan Toews were aging. Salary-cap constraints led to cost-cutting trades that depleted their roster. Defenseman Duncan Keith was traded to the Edmonton Oilers at his request to be closer to his family, leaving Chicago without a blue-line linchpin.

Then-general manager Stan Bowman saw an opportunity to address Keith's departure. On July 23, he acquired Seth Jones from the Columbus Blue Jackets, sending them young defenseman Adam Boqvist and three draft picks. He also signed Jones to an eight-year, $76 million contract.

Then 26, Jones had been a blueline stalwart with the Blue Jackets, logging big minutes while posting a career-best 57 points in 2017-18 and 46 points the following season. He played a crucial role in the best stretch of the Blue Jackets history, helping them reach the playoffs in four straight seasons from 2016-17 to 2019-20.

Acquiring Jones, however, wasn't enough to turn Chicago's drained roster into a contender again. They changed management in 2021-22 and under new GM Kyle Davidson have been engaged in a major roster rebuild. Toews and Kane are no longer with the team, leaving Jones as their highest-paid player.

Now 29, Jones has played well throughout the roster changes, tallying 37 points in 2022-23 and 31 points in 67 games last season. Nevertheless, he will be past his playing prime by the time Chicago's rebuilding roster is ready to become a contender in four or five years.

Jones' contract is considered to be among the league's worst. His $9.5 million average annual value takes up considerable cap space and could hamper their efforts to re-sign promising young players like Connor Bedard. It also makes him difficult to trade, as does his full no-movement clause.

Calgary Flames Acquire Jonathan Huberdeau From The Florida Panthers

On July 20, 2022, The Athletic reported Matthew Tkachuk informed the Calgary Flames that he wouldn't sign a new contract with them. Two days later, they traded the restricted free-agent winger to the Florida Panthers for left wing Jonathan Huberdeau and defenseman MacKenzie Weegar.

This swap worked out great for the Panthers. Tkachuk signed an eight-year contract and swiftly became one of their top stars. He led them to the 2023 Stanley Cup Final and helped them win their first Cup earlier this spring.

It also seemed like a great return for the Flames at the time. Huberdeau was coming off a career-best 115-point performance and was considered among the league's best playmakers. Meanwhile, the puck-moving Weegar reached a then-career-best 44 points in 80 games. Both signed lucrative long-term extensions with the Flames later that year.

Weegar fit in well on the Flames blueline, tallying a career-best 20 goals and 52 points last season. Huberdeau, however, has struggled since going to Calgary. He managed 55 points in 79 games in 2022-23. It didn't get any better for the 31-year-old winger last season, netting 52 points in 81 games.

The decline in Huberdeau's production coincided with the Flames' difficulties adjusting to the loss of Tkachuk and linemate Johnny Gaudreau, who signed with the Columbus Blue Jackets in 2022 as a free agent. After a 111-point season in 2021-22 (the second-best record in franchise history), the Flames missed the playoffs the next two seasons.

Huberdeau isn't primarily to blame for the Flames' decline, which resulted in management, coaching, and roster changes. Nevertheless, his offensive woes were a contributing factor. He's now entering the second season of his eight-year contract with an average annual value of $10.5 million and a full no-movement clause for the duration of his deal.

Given his age, Huberdeau's best seasons are likely behind him. If so, the Flames have a declining asset with a long, expensive contract that is nearly impossible to move taking up a big chunk of their cap space until 2031.