The Florida Panthers twice came back from a one-goal deficit to defeat the Washington Capitals 3-2 in overtime, tying the series at 2-2.

Heading into the contest trailing 2-1, and playing on Washington's home ice, the Panthers were put on the back foot early after T.J. Oshie opened the scoring in the first period.

Carter Verhaeghe tied things up less than 10 minutes later, before Evgeny Kuznetsov put the Capitals back in front in the third period off an assist from legendary teammate Alex Ovechkin.

With just over two minutes to play, Sam Reinhart tied it at 2-2 to force an extra period, where Verhaeghe would slot the winner five minutes in to steal the game on the road.

Speaking to post-game media, two-goal hero Verhaeghe said the result adds to the belief of what this team – dubbed the 'Comeback Cats' – can accomplish.

"We wanted to come in and have our best game of the series, and I think we did a pretty good job," he said.

"It’s just kind of a building block. We know we have another level to get to, and we’re a great team, so I think it’s just building some confidence."

Fellow goal-scorer Reinhart added that the backs-to-the-wall nature of the battle was everything he enjoyed as a competitor.

"Those are the kind of situations you want to be in as a hockey player," he said. "It’s a game that can really go either way at the end of it – we stuck with it, and we’re happy with the result."

Washington's Ovechkin – a three-time Hart Memorial Trophy winner for league MVP – was clear about the next course of action, and not overreacting to a painful loss.

"At the end, it was bad bounces and it goes in," he said. "It is going to be a tough, long series, so move on. Forget about it, move on."

It was much smoother sailing for the Colorado Avalanche, beating the Nashville Predators 5-3 to sweep their series 4-0. J.T Compher and Cale Makar both collected a pair of assists each for the Avalanche.

The Pittsburgh Penguins received a vintage performance from future Hall-of-Famer Sydney Crosby as he slotted one goal and dished two assists in his side's 7-2 win against the New York Rangers, taking a 3-1 series lead in the process.

Lastly, the Calgary Flames won a crucial Game 4 on the road against the Dallas Stars 4-1 to tie their series at 2-2, despite Stars goaltender Jake Oettinger making 50 saves.

Pittsburgh Penguins captain Sidney Crosby was quick to back goaltender Louis Domingue, following their 5-2 loss to the New York Rangers on Thursday.

The Rangers tied their playoff series up at 1-1 after Pittsburgh's 4-3 win in triple-overtime at Madison Square Garden on Tuesday.

One of the key figures in that overtime win, Domingue was given a start by Penguins coach Mike Sullivan, but gave up key goals to Ryan Strome and Chris Keider via deflections.

Crosby backed his teammate following the loss, bringing saves he did make with Game 2 in the balance in perspective.

"The fourth was a bad bounce, a couple of tips there," Crosby said. "I thought he [Domingue] was solid. I thought he made some big saves, especially when there was a one or two-goal difference, that kept us in it."

The two-time Hart Memorial Trophy winner believes the Penguins simply need to start better and put three periods of hockey together to progress past the Rangers.

"It's the playoffs," Crosby said. "There are going to be swings of momentum but I thought that in both games, as they've gone on, we've probably gotten better. We just have to find a way to come out of the gates a bit better.

"You don't want to get down two, we've done that a couple of times now. It's not something we want to make a habit of.

"We get that late one and we had some really good chances early in the third and didn't convert, and they got a bounce. That's what it came down to."

In other NHL playoff results on Thursday, a Cale Makar goal gave the Colorado Avalanche a 2-1 overtime win over the Nashville Predators, moving to 2-0 in their series.

Meanwhile, the Dallas Stars and Florida Panthers tied up respective series with the Calgary Flames and Washington Capitals.

Evgeni Malkin says the Pittsburgh Penguins "deserved to win" after he scored the decisive goal 5:58 into the third overtime of their 4-3 victory over the New York Rangers in the NHL playoffs on Tuesday.

The Penguins take a 1-0 lead in their Stanley Cup playoff opening-round series, where goalies Igor Shesterkin and Louis Domingue were outstanding for both sides.

Penguins back-up goalie Domingue came in for Casey DeSmith who exited due to cramping. Domingue starred with 14 saves in the second overtime and three more in the third.

"We know we can win every game if we play right," Malkin told reporters. "We play smart. We play hard. I think we deserved to win tonight."

The Rangers had led 2-0 after Andrew Copp doubled their lead in the second lead after Adam Fox's power-play goal in the first period.

The Penguins leveled it up after goals from Jake Guentzel in the second period, before Chris Kreider restored the Rangers' lead. Malkin found Bryan Rust to square the game up again, before it headed for overtime. Malkin came up with the decisive deflection.

The epic was the longest-ever NHL game played at Madison Square Garden.

On Domingue, Malkin added: "For me, I know Louis is unbelievable. He is big and he is fast. I wasn’t worried. It is hard to score on him in practice."

Washington Capitals forward Tom Wilson was injured as his side won 4-2 over the Florida Panthers in Game 1 of their series. Wilson had scored before going off with a lower-body injury.

Colorado Avalanche piled on five first-period goals as they routed the Nashville Predators 7-2 in Game 1 of their first-round playoff series.

Elias Lindholm's first-period goal proved the difference as the Calgary Flames got past the Dallas Stars 1-0.

Alex Ovechkin became just the third player to score 50 goals in nine different NHL seasons after adding two for the Washington Capitals in Wednesday's 4-3 overtime defeat to the Vegas Golden Knights.

Mike Bossy and Wayne Gretzky were the only players to previously reach that mark in nine separate campaigns.

"Obviously, it's pretty good company," Ovechkin said afterwards.

And the Capitals great took another record outright in the process, as the oldest player to score 50 goals in a season.

Ovechkin is 36, surpassing John Bucyk, who was aged 35 years and 327 days at the end of his 51-goal season in 1970-71.

It was special, too, for Ovechkin to achieve the feat at T-Mobile Arena, where he and the Capitals clinched the Stanley Cup Finals in 2018.

"Obviously, there's lots of great memories, locker room, everything, hotel," he said. "It's going stay here forever... yeah, pretty fun moments."

Ovechkin now has 780 career goals, still trailing Gretzky (894) and Gordie Howe (801).

New York Rangers great Henrik Lundqvist retired from the NHL after a stellar 15-year career in the league.

A five-time All-Star and Vezina Trophy recipient as the NHL's top goaltender in 2011-12, Lundqvist made the announcement on Friday.

Lundqvist signed a one-year deal with the Washington Capitals for the 2020-21 season, but the 39-year-old never made an appearance after undergoing open-heart surgery in January.

The Swede finished his NHL career with a 459-310-96 record, a 2.43 goals-against average, .918 save percentage and 64 shutouts in 15 seasons with the Rangers, while he went 61-67 with a 2.30 GAA, .921 save percentage and 10 shutouts in 130 Stanley Cup playoff games.

Lundqvist ranks sixth in NHL history in wins, seventh in saves (23,509), eighth in games played (887), ninth in starts (871), ninth in time on ice (51,816:51) and 17th in shutouts.

"Obviously there are a lot of emotions right now," Lundqvist said at a news conference in Sweden. "For me, it started here in Scandinavium when I was five years old I saw my first hockey game here. That's how it started.

"I also want to thank all the coaches and all the players that I've had the opportunity to play with and I want to thank all the clubs that I've represented. Jarpen, where it all starter, Rogle BK, Frolunda of course, and the New York Rangers. All of them have meant so much to me during that time and place. A big part of my life has been dedicated to those teams.

"At last I want to thank all the fans. I've felt so much support here at home playing for Frolunda and the national team, and in New York. It's been giving me so much joy to feel that support. I will be forever grateful for it. ... That is obviously something that I will miss, the intense feeling of being in a rink competing."

Initially drafted in 2000, Lundqvist enjoyed an outstanding rookie season in 2005-06, ranking fourth for save percentage (92.2 per cent) and fifth-lowest for goals against average (2.24). 

The 2011-12 campaign brought Vezina Trophy recognition as he kept eight shutouts in 62 games, again ranking fourth for save percentage (93.0 per cent) and fifth-lowest for goals against average (1.97). 

Lundqvist did enjoy success at international level with Sweden as he claimed a gold medal at the 2006 Winter Olympics and the 2017 Ice Hockey World Championships.

He is the Rangers' leader in wins, shutouts, games played, starts, saves, time on ice and goalie points (27, all assists). Lundqvist is also New York's postseason leader in wins, shutouts, games played, games started, saves and time on ice.

"It is with mixed emotions that The New York Rangers offer our best wishes and heartfelt gratitude to Henrik Lundqvist on the announcement of his retirement," the Rangers said in a statement. "Henrik's commitment to excellence made him one of the best goaltenders to ever play the game of hockey, and we are so fortunate to have witnessed his greatness firsthand for 15 years.

"As we congratulate Henrik on an extraordinary career and a lasting legacy of success, charity and character, we are honoured to announce that we will retire his number and raise his jersey to the rafters at an upcoming game this season. Henrik is, and always will be, a Ranger."

Alex Ovechkin’s pursuit of the NHL’s all-time record for goals scored will continue with the only franchise he has ever played for after the Washington Capitals re-signed their captain to a five-year, $47.5 million contract on Tuesday.

Ovechkin, drafted first overall by the Capitals in 2004, is the franchise leader in games played (1,197), goals (730) and points (1,320) since making his NHL debut in 2005-06. He led the Capitals to their first Stanley Cup championship in 2018.

Ovechkin’s $124 million, 13-year contract was set to expire before NHL free agency officially begins on Wednesday.

''Alex is the face of our franchise and is committed to this organisation and this city,'' Capitals general manager Brian MacLellan said. '

"'Alex embodies what our franchise is all about, and we're thrilled that he will continue his career in the Caps uniform for the next five years.''

Ovechkin’s 730 career goals rank sixth all-time behind Wayne Gretzky (894), Gordie Howe (801), Jaromir Jagr (766), Brett Hull (741) and Marcel Dionne (731).

Now signed through the 2025-26 season, Ovechkin – who turns 36 in September – would have to average nearly 33 goals per season during the life of his new contract to surpass Gretzky

Like everything else over the past year, the hockey world has been turned upside down by the coronavirus pandemic. The 2019-20 season was completed with teams playing in bubble locations in Toronto and Edmonton and the 2020 campaign will open without fans as part of a condensed 56-game season, among a slew of other changes. 

With the previous season extending several months past the normal ending date, the league had little choice but to delay the start of 2021 and to find a way to make a shortened season work. The new plan is for the regular season to end on May 8, with the Stanley Cup awarded no later than July 9. 

Of course, nothing is set in stone anymore and the NBA and NFL have had to deal with countless COVID-19 issues, so the NHL expects similar problems to arise with the pandemic experiencing another surge. The league knows it may have to adapt and games will very likely need to be rescheduled. 

The NHL has already dealt with this, as the start of the season for the Dallas Stars had to be pushed back to January 19 after six players and two staffers tested positive for coronavirus. While the completion of last season in the bubble locations was virtually flawless, teams are playing in home arenas this season, increasing the chances of players becoming infected. 

To combat this, teams will be allowed to carry taxi squads of four to six extra players who will practice and be prepared to step in when needed. 

While there is less hockey to enjoy, there are some tweaks to the upcoming season that fans will enjoy. 

The four divisions have been realigned and they include an all-Canada division of seven teams, made necessary by border restrictions. The other three divisions are mostly based on geography, but St Louis and Minnesota were shuffled into a division with the three California teams, Vegas, Arizona and Colorado. 

The Chicago-Detroit rivalry gets renewed with the Red Wings moving into the Central Division, and Tampa Bay and Dallas – last season's Stanley Cup Final participants – are now together in the Central.  

There should be no shortage of intensity this season with teams scheduled to play mostly back-to-back sets solely against teams in their own division. So, the Flyers and Penguins will meet eight times, as will the Islanders and Rangers and Kings and Ducks. The teams in the all-Canada division will face each other nine or 10 times.  

The first two playoff rounds will be played within the division, meaning the bad blood that started in the regular season could grow even deeper. The division winners will then advance to the semifinals but seeding will be based on points rather than geography.  

The new setup raises the possibility of a Stanley Cup Final between traditional East teams like the Capitals and Penguins or Canadian rivals Montreal and Toronto.   

To recoup some of the money lost by having no fans or limited fans at the start of the season in some cities, the NHL is allowing teams to include a sponsor name on their helmets and each division will also include the name of a corporate sponsor. 

The condensed season was preceded by an abbreviated training camp without exhibition games and there is concern that the start of the season will be marred by sloppy play. This could be especially true for the seven teams that have not played a game since March after they did not qualify for the expanded playoffs.  

As in any offseason, several big-name players changed teams. It will be jarring to see 43-year-old Zdeno Chara in a Capitals uniform and Joe Thornton playing for the Maple Leafs after 14 seasons in San Jose. Henrik Lundqvist would have looked strange as a member of the Capitals following an 887-game run with the Rangers, but he decided not to play this season due to a heart condition. 

Injuries will also keep some marquee players off the ice for a while. Lightning forward Nikita Kucherov – the 2018-19 scoring leader – will miss the entire regular season due to hip surgery and the Stars could be without top forward Tyler Sequin (hip) and goaltender Ben Bishop (knee) until at least March.  

Blackhawks captain Jonathan Toews is out indefinitely with an unknown illness and there is no word on whether the 12-time 20-goal scorer will play this season. 

While this season is full of unknowns and will be like no other before it, the potential is there for it to be one of the most exciting in recent memory.