[RELATED: Senators-Bruins coverage | Smith is Senators' X-factor | Why Bruins will win Cup]

How they got here

The Ottawa Senators (44-28-10), who finished second in the Atlantic Division, face the Boston Bruins (44-31-7), who finished third in the division to return to the Stanley Cup Playoffs for the first time since 2014.

The best-of-7 Eastern Conference First Round series begins at Canadian Tire Centre on Wednesday (7 p.m. ET; NHLN, SN, TVA Sports).

After missing the playoffs last season, Ottawa returns to the postseason under new coach Guy Boucher. Boston has its own new coach, Bruce Cassidy, who replaced Claude Julien on Feb. 7. Though the Bruins have missed out on the playoffs each of the past two seasons, they won the Stanley Cup in 2011 and reached the Final in 2013. The Senators last made the Cup Final in 2007.

Video: Senators vs Bruins First Round Preview

5 storylines

Overcoming adversity: That has been the tagline for the Senators, whether it was the post-concussion syndrome of forward Clarke MacArthur, the cancer goaltender Craig Anderson's wife faced, or the many, many injuries that kept players out during the regular season, most recently the foot injuries to defenseman Erik Karlsson. Once the playoffs arrive, the question is whether going through all of that this season, and staying together, will bear fruit for the Senators, who might be the healthiest they've been all season heading into this series.

Can Brad Marchand bounce back?: It was a disappointing end to what had been the best season of the left wing's NHL career. Marchand soared to the top of the NHL scoring race, at one point late in the season tying Sidney Crosby in goals, on his way to being mentioned in the Hart Trophy conversation. But Marchand finished the season in the press box, suspended by the NHL Department of Player Safety for the final two games of the season after spearing defenseman Jake Dotchin of the Tampa Bay Lightning. It left a bad taste for the Bruins, and it left Marchand one goal shy of the 40 he had told general manager Don Sweeney he would score this season after signing an eight-year contract in September.

Video: FLA@BOS: Marchand roofs a rebound for PPG

Keeping it close: The Senators' success this season was all about the system, all about slowing down the game and slowing down the opposition. They weren't exactly a team that won by blowing out opponents, but rather by adhering to their defensive-minded approach. The question in the playoffs will be whether that system works for them in a best-of-7 series like it did in the regular season. It appeared that the Bruins figured out a key to playing the Senators in their final regular-season matchup, even though Boston lost 2-1 in a shootout, so that will be key to watch as well.

Enough defense: The question all season was whether the Bruins defense would be good enough. Now, after defensemen Torey Krug and Brandon Carlo each was injured in the final two games of the regular season, the question is whether they'll be healthy enough. There's no way to win the Stanley Cup, or even a round, without a good defense, and integrating inexperienced defensemen or moving players from the press box into the rotation is far from optimal at this time of year.

Coach vs. coach: The coaching matchup is an interesting sidenote to this series. Neither coach was in the NHL at this point last season, and yet each has led his team to the postseason. Boucher, who is in his fourth season as an NHL coach, is 11-7 in his career in the Stanley Cup Playoffs, having guided the Tampa Bay Lightning to the Eastern Conference Final in 2011. He has not been back since. For Cassidy, it's been even longer. The Bruins coach was 2-4 with the Washington Capitals in the 2003 playoffs, when his charges bowed out in the first round to the Lightning. That's not a lot of playoff experience on either side.

By the numbers

0.92: Karlsson's points-per-game average this season. He was edged by Brent Burns (0.93) of the San Jose Sharks for first among NHL defensemen but led the Senators; Mike Hoffman was second (0.82). Karlsson needed six more points in 77 games this season to match his NHL career high of 1.00 points per game, which he set last season with 82 in 82 games.

85: The number of points for Marchand this season. He became the first Bruins player to top 80 points since Marc Savard had 88 in 2008-09.

85.7: Boston's penalty-kill percentage, the best in the NHL. Going up against the Senators, who were 23rd on the power play (17.0 percent), should mean Boston has the advantage when Ottawa is on the man-advantage. But the Senators have one powerful weapon who can turn things around at any moment: Karlsson, who had 27 power-play points (four goals, 23 assists) in 77 games.

In the spotlight

Senators: Craig Anderson, goaltender -- It's been a difficult and emotional season for Anderson, whose wife Nicholle went through cancer treatment, with the goaltender going on indefinite leave to be with her. He returned to the Senators on Feb. 11. Anderson was 13-5-3 with a 2.12 goals-against average and .929 save percentage after returning. He is 12-14 with a 2.35 GAA and .933 save percentage in 27 NHL playoff games.

Video: NYR@OTT: Anderson knocks down laser from Hayes

Bruins: David Pastrnak, forward -- Pastrnak, in his third season in the League, made the jump to elite status this season. He had NHL career highs in goals (34), assists (36) and points (70) to finish second on the Bruins in scoring. But he has yet to experience Stanley Cup Playoff hockey after the Bruins missed the postseason in each of his first two seasons, so it will be a test for him, whether he can raise his game in the most important of moments. If he can, that will go a long way toward boosting the Bruins to a series win.

Video: TBL@BOS: Pastrnak slams Nash's feed past Vasilevskiy

Keys to victory

Senators: Keeping it close. As multiple Senators mentioned after they clinched a playoff berth in a 2-1 shootout win against the Bruins on Thursday, the reason they defeated Boston that night and the reason they had succeeded all season was their ability to play a tight-checking, close game. They defeated the Bruins just that way all season, winning three one-goal games and one two-goal game.

Bruins: Breaking out. The Bruins have played a puck-possession game all season, one that can break out offensively at any time, especially when led by Marchand and Pastrnak. To win the series, Boston will have to break through the Ottawa defensive morass and use the firepower that they have to overpower the Senators' system.