NHL Playoff Schedule 2018: Stanley Cup Guide, Postseason Tree and Standings

The first round of the Stanley Cup Playoffs has reached the critical stage.

Four series were decided early, meaning the Vegas Golden Knights, San Jose Sharks, Winnipeg Jets and Tampa Bay Lightning have advanced to the second round. Vegas and San Jose registered first-round sweeps, while Winnipeg and Tampa Bay won their respective series in five games.

Four other series are much closer, although the Pittsburgh Penguins, Nashville Predators and Boston Bruins were all in a position to win their battles in five games. However, all three lost potentially decisive games at home.

The Washington Capitals have battled back from a 2-0 deficit to take a 3-2 series lead, and they can win their series against the Columbus Blue Jackets if they win on the road in Game 6 on Monday night.

The Penguins and Philadelphia Flyers will play Game 6 on Sunday at 3 p.m. ET on NBC. That game will be played in Philadelphia, and if the Flyers can win to extend the series, the seventh game would be played Tuesday in Pittsburgh.

Gene J. Puskar/Associated Press

The Colorado Avalanche may be the most surprising team in this year's playoffs because they were the No. 8 seed in the Western Conference. The Avs rallied from a late 1-0 deficit in Game 5 in Nashville to beat the top-seeded and Presidents' Trophy-winning Predators 2-1 Friday night. They will host Nashville on Sunday night, and a win would force a decisive seventh game Tuesday in Nashville.

The Bruins dominated the territorial game against the Toronto Maple Leafs on Saturday night, but a shaky game from goaltender Tuukka Rask cost them a chance to close out the series. Toronto built a 4-1 lead in the second period and withstood a furious Boston rally to earn a 4-3 victory.

Boston had 45 shots on goal compared to the Maple Leafs' 21, but Frederik Andersen stopped a number of point-blank Boston opportunities in the third period to keep the Bruins from tying the score. Andersen also received a big assist from Toronto's defense, as the Maple Leafs blocked 22 Boston shots, compared to eight blocks by Boston's defense.

Connor Brown, Andreas Johnsson, Tyler Bozak and James van Riemsdyk all scored for the Maple Leafs, and Van Riemsdyk's goal at 11:55 of the second period drove Rask from the net in favor of backup Anton Khudobin.

David Backes, Sean Kuraly and Noel Acciari scored for the Bruins, with the top line of Patrice Bergeron, Brad Marchand and David Pastrnak being kept off the board.

"They were coming hard, they wanted to tie it up and I think we might have been playing a little too much on our heels," Brown said, per Matt Kalman of NHL.com. "It's important to keep going to get them and keep playing in their end. They were breaking out a little easier than we would have liked, but at the end of the day, we got a gutsy win down the stretch, and it's a real momentum-builder."

Sunday's Stanley Cup Schedule

Pittsburgh Penguins at Philadelphia Flyers, 3 p.m., NBC. Pittsburgh leads series 3-2.

Nashville Predators at Colorado Avalanche, 7 p.m., NBCSN. Nashville leads series 3-2.

All times ET.

Updated Playoff Standings

Eastern Conference

Tampa Bay Lightning defeated New Jersey Devils 4-1. Tampa Bay will face winner of Boston-Toronto series.

Boston Bruins lead Toronto Maple Leafs 3-2. Game 6 at Toronto, Monday, 7 p.m. ET., NBCSN.

Washington Capitals lead Columbus Blue Jackets 3-2. Game 6 at Columbus, Monday, 7:30 p.m., CNBC.

Pittsburgh Penguins lead Philadelphia Flyers 3-2. Game 6 at Philadelphia, Sunday, 3 p.m., NBC.

Western Conference

Nashville Predators lead Colorado Avalanche 3-2. Game 6 at Colorado, Sunday, 7 p.m., NBCSN

Winnipeg Jets defeated Minnesota Wild 4-1. Winnipeg will face winner of the Nashville-Colorado series.

Vegas Golden Knights defeated Los Angeles Kings 4-0. Vegas will face San Jose in second round. Dates and times to be announced.

San Jose Sharks defeated Anaheim Ducks 4-0. San Jose will face Vegas in second round. Dates and times to be announced.