The Capitals, who were 2-0-2 against the Flyers in the regular season, are hoping for a longer playoff run than the last time they finished with the best record in the NHL; Washington lost to the Montreal Canadiens in the first round in seven games in 2010.
The Capitals' core, led by Alex Ovechkin, has never advanced to the conference final. They blew a 3-1 series lead to the New York Rangers in the second round last year.
Video: Flyers face off with Caps in Round 1 of the playoffs
Evgeny Kuznetsov's five assists (five points) led Washington against Philadelphia, and Ovechkin scored two goals. Goalie Braden Holtby had a 2.21 goals-against average and .926 save percentage in the four games.
Ovechkin has been dominant against the Flyers in his career; he has 48 points (31 goals) in 41 games.
The Flyers have not been in the playoffs since 2013-14, when they lost to the Rangers in seven games in the first round.
Claude Giroux's four points (goal, three assists) led Philadelphia against Washington, and Brayden Schenn and Jakub Voracek each had two goals. Goalie Steve Mason was 1-2-0 with a 2.94 GAA and .902 save percentage.
It will be the first playoff series between the Capitals and Flyers since 2008; Philadelphia won when Joffrey Lupul scored in overtime in Game 7. Philadelphia has won three of five postseason series against Washington.
Capitals: Washington was one of six NHL teams that had five players with 50 or more points this season: T.J. Oshie (51), Justin Williams (52), Nicklas Backstrom (70), Ovechkin (71) and Kuznetsov (77).
Ovechkin skates with Backstrom at center and Oshie on the right wing on the first line. Traded to Washington in July, Oshie scored an NHL career-high 26 goals, the most by a Capitals player other than Ovechkin since 2010-11. He balances out the top line with his combination of skill and scoring ability.
Kuznetsov is capable of taking over a game, and his exceptional playmaking ability makes him dangerous in any situation. Kuznetsov is flanked by Andre Burakovsky and Williams, another offseason acquisition. The Capitals signed Williams for his playoff experience and ability to perform under pressure. Burakovsky struggled in the early part of the season and at times played in the bottom six before finding a groove playing with Kuznetsov and Williams.
Coach Barry Trotz has flipped these combinations during the season, and the Capitals pride themselves on easily adapting to different linemates.
Besides its obvious offensive firepower, Washington has something that was missing in years past: depth down the middle. Beyond Backstrom and Kuznetsov, the bottom six has several center options: Mike Richards, Marcus Johansson, Jay Beagle and Daniel Winnik. Each can play wing too. Those players probably won't show up on the score sheet very often, but each of these utility-type players is willing to do whatever is asked of him.
Flyers: Philadelphia's top line for most of their playoff push had Giroux centering Schenn and right wing Wayne Simmonds.
Giroux is the heartbeat of the Flyers, playing a 200-foot game, producing in all three zones and taking all the important faceoffs. His 366 points since the 2011-12 season lead the NHL, and he won 57.5 percent of his faceoffs in 2015-16.
Simmonds and Schenn each had his best NHL season. Simmonds reached 30 goals for the first time and has developed into one of the top net-front players in the League, with nearly half his 32 goals coming from 10 feet or closer to the net.
Sean Couturier centers the second line. He's used against the opposition's top line but raised his game offensively this season, setting personal NHL bests in assists (28) and points (39).
Voracek is getting back into gear since returning March 16 from a three-week absence because of a lower-body injury. He played with Couturier at right wing but also saw time at left wing with Giroux and Simmonds.
The bottom two lines are filled with speed and grit. Matt Read is a two-time 20-goal scorer, and Sam Gagner showed an improved offensive touch the second half of the season.
The fourth line of Pierre-Edouard Bellemare, Chris VandeVelde and Ryan White is an energy group that prides itself on speed and a heavy forecheck, but White set an NHL career-best with 11 goals, nearly double his previous high.
Capitals: Injuries to defensemen plagued Washington for much of the season, but depth at the position allowed them to continue their Presidents' Trophy run without missing a beat.
John Carlson is back to playing big minutes since his return from late-season surgery. He missed 13 games but came back for the final 10. Carlson was paired with Nate Schmidt before Trotz put him back with Brooks Orpik, and he continues to get time on the top power-play unit.
Schmidt took on some of Carlson's minutes when he was injured early in the season and during his recovery from surgery; he is capable of handling a heavier workload against tougher opponents.
Orpik missed extended time with injury this season but began playing with Dmitry Orlov while Carlson was injured. Orlov is a high-risk offensive defenseman and can be prone to errors in the defensive zone.
Two players who have been on the same pair since last season are Karl Alzner and Matt Niskanen. Alzner is a seasoned penalty-killer riding a streak of 459 consecutive games. Mainly a stay-at-home type player, he's not known for his scoring ability but can occasionally contribute; Trotz's system encourages defensemen to jump into a play if they can. Niskanen has an offensive upside he doesn't often get to show, but he's one of the Capitals' more versatile defensemen. He can play shorthanded and on the power play.
Mike Weber and Taylor Chorney are depth defensemen able to step in when needed.
Flyers: Rookie Shayne Gostisbehere's arrival on Nov. 14 changed Philadelphia's season. The Flyers are averaging nearly 0.75 more goals per game with him in the lineup, and their power play percentage has gone up six points since his arrival. He struggles in the defensive zone, especially against bigger forwards and heavy forechecks, but his offensive skill makes up for any deficiencies.
"He's certainly given us a lot," general manager Ron Hextall said. "When he's got the puck, he's very savvy. He makes a lot of plays. He gets the puck to the net, he can skate the puck out of trouble. He can pass the puck out of trouble. He's done a good job for us."
The Flyers also depend on Mark Streit to supply offense from the defensive end.
Andrew MacDonald, Nick Schultz, Radko Gudas and Brandon Manning contribute more in the defensive zone, although Gudas had an NHL career-best five goals.
As a unit, defending against teams with strong cycle games has been difficult, and breakouts sometimes can take multiple passes. Turnovers have a tendency to happen at inopportune times.
Evgeny Medvedev provides depth. He was signed as a free agent last summer with the hope of adding more puck-moving skill, but he's had a tough time adjusting to the speed and smaller rink size in North America, and didn't play much in the final six weeks of the regular season.
Video: NYI@WSH: Holtby denies Okposo's one-timer
Capitals: Holtby didn't lead the NHL in save percentage or goals-against average, just the statistic he considers the most important: wins.
And he's not been shy about discussing his preference to play as often as possible. Holtby's 66 games were third in the NHL after his 73 led the League last season. Trotz managed his starting goaltender's workload shrewdly, probably a wise choice for a team planning a deep playoff run.
In his first full season in Washington, Philipp Grubauer provided a trustworthy option at backup when he did get a chance to play. His starts were scarce due to Holtby's workload, but he allowed the Capitals more flexibility to manage their goaltenders.
Video: PIT@PHI: Mason snags Mouillierat's shot from in close
Flyers: Philadelphia rode Mason down the stretch. He started 13 of the final 14 games and on most nights was the Flyers' best player.
"He's a great goalie, one of the top in the League, and he's been like that for the last two years," Voracek said. "It's a tough stretch for him because of so many games played but he's enjoying it. He's riding a hot streak, he's playing well, he is playing confident."
Mason said he's adjusted his practice time and gotten enough rest to get through the heavy workload.
"It would be a lot more difficult if we weren't in the playoff race," he said. "When you're playing for something meaningful, it's a lot easier."
Michal Neuvirth is healthy after missing three weeks because of a lower-body injury. He'll be the backup but had a top-five save percentage in the League among goaltenders to play at least 30 games.
The Flyers allowed 2.57 goals per game with Mason and Neuvirth as their goalies, down from 2.72 last season when Mason and Ray Emery played most of the games.
"[Mason] has kept us in every single game and that goes along with [Neuvirth] too," Simmonds said. "They've given us a chance to get our feet underneath us and play better hockey."
Capitals: Trotz has never advanced past the second round of the playoffs during his 17-season NHL coaching career. He's also never been at the helm of a team with expectations as high as the Capitals. Although that may be new territory for him, Trotz has been able to instill his trademark level-headed, business-like approach in the Capitals. The result is a mature, nearly unflappable group of players poised to take the next step. All Trotz needs to do is what he's done all season.
Flyers: Hakstol never wavered in his belief in his system or in his players' ability to play it. After a slow start, the Flyers were one of the best teams in the League down the stretch.
"Dave treated his payers at North Dakota like men, like pros," Hextall said. "His transition to this level was a lot quicker, I think, than a lot of guys."
Hakstol showed a deft touch with player deployment, from moving Voracek to left wing -- a position he had never played -- in December to get his season going, to showing a growing confidence in Gostisbehere despite struggles in the defensive zone. He also helped Schenn and Couturier each take big steps in his development.
Hakstol's public demeanor never changes after wins or losses. He's small-picture focused with a belief that if enough of the little things are done right, the big picture will take the proper shape.
"To [Hakstol's] credit, he listens to people," Hextall said. "A smart person listens to people. A smart person doesn't know it all."
Video: WSH@LAK: Oshie nets PPG, puts Capitals on the board
Capitals: Washington has been consistently at or near the top of the standings in power-play percentage the past few seasons, and 2015-16 was no exception. The power play ranked fifth in the NHL at 21.9 percent.
Ovechkin might be the most dangerous player in the NHL on the power play, but the addition of Oshie to the top unit brings another scoring option. If Ovechkin is tied up, Oshie is probably open.
The Capitals roster is deep enough to spread the talent around to the first and second power-play units.
The penalty kill, which has the defensive-minded Trotz's fingerprints all over it, has been effective. A regular on the kill, Richards has turned the defensive aspect of his game into his bread and butter and is always a threat for shorthanded goals.
Video: PHI@NYI: Gostisbehere buries wrister from the point
Flyers: Philadelphia has one of the most gifted first power-play units in the League. Giroux runs things from the half-wall on the left side. Simmonds' 59 power-play goals since the 2011-12 season are third in the League. Gostisbehere's big shot from the point has added an important element.
The second unit has been more productive this season, in part because Streit is at the point and Couturier's improved offensive game.
Bellemare and VandeVelde generally are the first pair of penalty-killing forwards over the boards. They've done a solid job using smarts and speed to read plays and break up passes. Bellemare, Couturier and Giroux take the bulk of the important faceoffs, and usually have done well. When pucks have gotten through, though, the defensemen have had trouble clearing the front of the net.
Capitals: Evgeny Kuznetsov, forward -- Kuznetsov has established himself as one of the top players on this iteration of the Capitals, and rightfully so. This year, it's not Ovechkin who led the Capitals in points; it was the 23-year-old Kuznetsov.
In his second season at center, Kuznetsov scored 20 goals for the first time in his NHL career and his 57 assists ranked fourth in the League.
He didn't score a goal in the final 20 games but had 12 assists. When he goes behind the net, good things usually happen. He can break any game wide open.
Flyers: Jakub Voracek, forward -- Voracek was fourth in the League in scoring last season but never got close to that level in 2015-16. He had one goal in his first 30 games, and it took a move to left wing to energize him. In 29 games between Dec. 15 and Feb. 25, when he sustained a lower-body injury, he had 31 points. He didn't find that pace after returning, but if he can get close to being the Voracek of last season, or the one from midseason, he can provide some spark to the offense at 5-on-5 and on the power play.
"I think Jake's working hard and I don't think he's hit his stride," Hakstol said. "... I think he's got another level to get to yet. Hopefully, he'll keep pushing toward that."
WILL WIN IF ...
Capitals: Holtby is able to maintain his form and keep playing at a high level. He was often the best player on the ice for the Capitals and could compensate well for their frequent slow starts. Their success often depends on him.
Though things seem to be trending upward as far as their penchant for sluggish first periods, the Capitals can't fall back into old habits of playing catch-up in every game during the postseason.
Granted, the Capitals were miles ahead of the rest of the League for most of the season and the first team in the NHL to clinch a playoff berth. For more than a month, they haven't had much to play for, but if they can rekindle a sense of urgency, they could be unstoppable.
Flyers: Mason remains their best player. While the skaters in front of him looked fatigued during the final few games of a very tough stretch to end the regular season, Mason never wavered.
"It looks like he's getting better every game, if that's possible," Giroux said.
Despite the fatigue and inconsistencies in their game, the Flyers know Mason will stop most of the pucks that come his way, and having that confidence in a goaltender can be inspiring and relaxing. So if Mason can maintain his level, he can pull the rest of the team up along with him.