The Pittsburgh Penguins had to work a lot harder than anyone thought they would to get past the New York Islanders in the first round of the Stanley Cup Playoffs. Their next hurdle figures to be even tougher.

Though the Ottawa Senators were seeded seventh, they didn't play like a lower seed. They dominated the Montreal Canadiens in the first round with a physical style of play, one much like the Islanders used to make life miserable for the Penguins.

Pittsburgh swept Ottawa in their three-game season series. On Jan. 27, Evgeni Malkin registered the winning goal in a 2-1 shootout victory. It came against Ben Bishop, who was later traded to the Tampa Bay Lightning.

On Feb. 13, the Penguins won 4-2 on the strength two goals by James Neal and one each from Pascal Dupuis and Sidney Crosby.

On April 22, the Penguins won 3-1. Dustin Jeffrey, Jarome Iginla and Taylor Kennedy had the goals for the Penguins, and backup goalie Tomas Vokoun stopped 34 of 35 shots to outduel Craig Anderson.

That doesn't mean the Penguins expect an easy time in round two.

"We've played them in the past and they always battle," Dupuis said. "Their building gets shaking at times. They're a team that obviously played well in the first round and beat Montreal, [a] seven [seed] beat a two [seed]. So it should be a good matchup."

The Penguins will have to find ways to solve Anderson if they hope to win the Eastern Conference Semifinal series. Anderson was Ottawa's best player against Montreal, stopping 171 of 180 shots for a .950 save percentage. If he does that again, the Senators could pull their second upset of the playoffs.

Ottawa will have to shut down Pittsburgh's big guns. Crosby had three goals and nine points in five games against the Islanders after returning from a broken jaw; Iginla scored twice and added seven assists; and Dupuis scored five times in the six games.

Pittsburgh got a tougher-than-expected test from the Islanders, whose speedy forwards put a lot of heat on the Penguins' defense. Crosby said his team can expect more of the same from the Senators.

"They're playing good hockey; they're pretty similar [to the Islanders]," Crosby said. "They have some fast forwards, a lot of skill, a lot of speed. We're going to have to do a better job of keeping the puck out of our end and out of our net."

The Senators and Penguins met three times in the Stanley Cup Playoffs, with Ottawa winning a first-round series in five games in 2007 and Pittsburgh sweeping in the opening round in 2008, each team using its victory as a starting point to a trip to the Final. They met in the first round again in 2010, with Pittsburgh winning in six games, including three victories at Ottawa.

As if the series needed any extra juice, there figures to be plenty of hard feelings from the Feb. 13 meeting -- that was the night when Penguins forward Matt Cooke delivered a hit to Senators defenseman Erik Karlsson that resulted in the reigning Norris Trophy winner suffering a 70-percent tear of his Achilles tendon. Karlsson missed 31 games but returned right before the end of the regular season.

As expected, Pittsburgh has an embarrassment of riches at forward.

The Penguins have four of the top seven scorers in the playoffs after the first round. Malkin (two goals, 11 points), Iginla (two goals, nine points) and Dupuis (five goals, seven points) each made the score sheet in every one of the six games in the first-round series. Crosby (three goals, nine points) played in five of the games and had at least a point in each of his appearances.

That list is still missing Chris Kunitz and James Neal, who combined to score 43 goals and 88 points in the regular season. In the first-round ouster of the Islanders, Neal had a goal and Kunitz added two goals and three assists.

Pittsburgh's forwards combined for 19 goals in the six games of the series.

Even Pittsburgh's so-called depth forwards have been very good.

Brandon Sutter excelled in a checking role in the first round, and Brenden Morrow and Cooke were physical forces throughout the series. Joe Vitale and Tyler Kennedy were late additions to the lineup, joining in Game 5, but they added speed and grit to the rotation, and Kennedy scored the winning goal in Game 5.

How deep are these Penguins? Jussi Jokinen, who had 11 points in 10 regular-season games, can't crack the lineup. Neither can rookie Beau Bennett, who scored in Game 1 but lost his job by Game 3.

This group is the Senators' biggest weakness when directly compared to the Penguins, but the Ottawa forwards are not to be taken lightly.

Daniel Alfredsson not only provides inspirational leadership, he's tied for the team lead in scoring and anchors the top line. His center, Kyle Turris, showed improvement with each game he played in the first round. Turris was demoted to the fourth line in each of the first two games against the Canadiens, then bounced back with a goal in each of the final three games. His performance at the end of Game 4, when he crashed the net to earn an assist on Cory Conacher's tying goal with 22.6 seconds to play then scored the overtime winner, was what allowed the Senators to win the series as quickly as they did.

The extra time off likely will help forwards Milan Michalek and Colin Greening, each of whom appeared to be playing with an injury that affected his production in the first round.

The depth of the group comes from its youth, with Jean-Gabriel Pageau emerging as perhaps Ottawa's fastest and most dangerous player, and Conacher, Jakob Silfverberg and Mika Zibanejad each had their hero moments in the first round.

But the line that may have been the most important against the Canadiens was centered by Zack Smith with Chris Neil and Matt Kassian on the wings, a trio that exacted a physical toll on the Montreal defense and provided the team with a good dose of energy with nearly every shift. Letang could see a steady dose of these three.

Letang was the anchor the Penguins have come to expect on the blue line, continuing the Norris Trophy-worthy campaign he fashioned in the regular season. This time, though, he has some help from Paul Martin, who is rounding into form after battling injuries.

Letang had a pair of goals and six points against the Islanders, but just as importantly played more than 27 minutes a game and was a plus-3. Letang had a point in five of the six games. Martin averaged 26:12 per game and had six points, going a plus-5. His only goal of the series tied Game 6 at 3-3 to set the stage for the winner by defenseman Brook Orpik.

Orpik returned in Game 4 and averaged more than 23 minutes per outing in his three appearances. His goal was his first in 78 Stanley Cup Playoff games. The unlikely goal-scoring included Douglas Murray, imported at the NHL Trade Deadline, who had two goals in the first round.

The bottom third of the Penguins' rotation has been a little more troublesome. Matt Niskanen played in all six games but struggled at times against New York's speed. Mark Eaton and Deryk Engelland had shots in the lineup but could not stick. Simon Despres is manning the No. 6 spot because coach Dan Bylsma likes his speed and puck-moving ability.

The Senators defense may be best-known because of the offensive wizardry of  Karlsson, but really it is defined by the fact it is big, mean and mobile. Marc Methot (6-foot-3, 231 pounds), Jared Cowen (6-foot-5, 230), Chris Phillips (6-foot-3, 221) and Eric Gryba (6-foot-4, 222) were able to skate with the speedy Canadiens forwards in Round One. And once they caught up with them, they hit them -- often. Their mission in this series will be to wear down the highly skilled Penguins at every opportunity.

Offensively, Karlsson is clearly still recovering from the injury he sustained when Cooke tried to pin him against the boards but instead had his skate land on the back of Karlsson's leg. Karlsson's skating is not where it was before the injury and he appeared to tire with every game against the Canadiens.

Still, he's tied with Alfredsson for the team scoring lead with six points (one goal and five assists) and averaged a team-high 26:49 per game, including a League-best 6:15 per game on the power play. The extra rest the Senators earned by dispatching the Canadiens in five games will benefit Karlsson more than anyone.

Karlsson and Sergei Gonchar form a dangerous power-play duo on the points, and they eat up nearly all of the available minutes with the man advantage.

Goaltending is again proving to be Pittsburgh's bugaboo.

After a great showing in Game 1, Marc-Andre Fleury started fighting and fumbling the puck, suffering through a three-game run that saw him allow 14 goals, several of which were downright ugly. In the process, he fumbled his hold on the starter's job.

Bylsma was forced to turn to backup Tomas Vokoun for Game 5 and the 36-year-old responded with a 31-save shutout. He also played Game 6 and was equally strong despite allowing three goals.

Now Bylsma faces a crucial decision. Does he go back to his franchise goalie who seems to be facing a crisis of confidence after allowing a series of "bad" goals, particularly in losses during Games 2 and 4? Or does he ride the hot hand of Vokoun, who has 13 games of playoff experience now?

The answer may define the postseason for the Penguins.

Anderson was the Senators' MVP of the first round, and it could be argued there was no single player across the NHL who was more responsible for his team's series victory.

His .950 save percentage is impressive enough, but it doesn't tell the entire story. It was the timeliness of Anderson's brilliance that was the key to his and his team's success.

Anderson did not allow a third-period goal on 40 shots in five games while the Senators scored 12. But what was perhaps even more important was Anderson's play in the first period, when he allowed two goals on 66 shots for a .970 save percentage, allowing the Senators to score the first goal in three of the five games.

Ottawa had what could be considered a strong start in one of the five games they played against Montreal, and Anderson was what allowed them to weather the initial storm. It was a mental advantage in the series that was immeasurable.

Anderson's backup is no slouch either. Robin Lehner had a 2.20 goals-against average and .936 save percentage in 12 games during the regular season. But the Senators will go as far as Anderson brings them.

Bylsma has won the Stanley Cup, so that gives him instant credibility any time he is in this tournament.

And Bylsma has already made some tough changes. Not only did he go to Vokoun in Game 5, but he subbed out three struggling players: Bennett, Jokinen and Eaton. Kennedy, one of the replacements, scored the winning goal in Game 4.

Bylsma also switched up his top two lines to get certain players going and generate more favorable matchups. It is not always easy to move around star players, but Bylsma made the hard calls necessary.

Yet his legacy likely wil be determined by the decisions he makes about his goaltending for the rest of this tournament and how those decisions pan out.

Paul MacLean overcame injuries to key players to get his team into the playoffs, and once there he didn't stop making all the right moves.

He played a significant role in getting the Senators past the Canadiens, benching players when they weren't effective and promoting anyone who was playing well at the time, getting results each time.

Turris was demoted in Game 1 and 2 of the first round, then rewarded his coach in each of the final three games. Pageau was the one who replaced Turris on the top line each time, and he scored a hat trick in Game 3. Zibanejad and Conacher were benched for long stretches of Game 4 before they each scored in the third period to tie the game, leading to Turris' overtime winner.

MacLean's ability to recognize who is feeling it on a given night is one of Ottawa's main strengths.

Special teams likely were the biggest difference in the first-round series for Pittsburgh.

The Penguins seemed to score at will on the power play, with four goals in 13 power-play opportunities at home and three times in eight opportunities at the Nassau Coliseum to finish with a League-best 33-percent conversion rate.

Letang and Kunitz each had two power-play goals, and Crosby, Iginla and Bennett scored with the man advantage.

Pittsburgh's power play was made even more effective because of the efficiency the team displayed on the penalty kill.

In 20 times short, the Penguins allowed a pair of man-advantage goals -- one at home and one on the road -- to a very dangerous Islanders offense.

It will be interesting to see if the Pittsburgh penalty killers can keep that momentum going against an Ottawa team that feasted, at times, on the undisciplined ways of  Montreal.

The Senators' power play was a weakness in the final stretch of the regular season, going 4-for-56 across the final 14 games, including 1-for-12 in the three games Karlsson played.

There was some improvement in the first round of the playoffs, with a 20.4 percent success rate. However, five of the six power-play goals the Senators scored came on the tail end of blowout wins in Game 3 and Game 5. They will need the power play to work better when the game is on the line.

The Senators penalty kill has been strong all season and it continued to be in the playoffs, frustrating the Canadiens' top pairing of P.K. Subban and Andrei Markov into turnovers with their high-pressure style and proving very effective at puck retrieval on dump-ins, often preventing the Canadiens from setting up their offense.

Paul Martin: If he is on top of his game, as he was for long stretches in the first round, he makes an already deep Penguins team all the more deep by providing a skill set that is perfect for this team. Martin can skate all day,, he can create offense with his shot and his ability to read the play and create transition, and he can defend better than he is often given credit. If he does all those things well, the Penguins have two two-way pairings that become a matchup nightmare for opposing teams.

Erik Karlsson: It's a given that Anderson is the key to the series for the Senators, but if Karlsson is able to raise his game another notch in Round Two it will give Ottawa more than a fighting chance. Though he played heavy minutes against Montreal, Karlsson got worse as the series moved along. After missing two-and-a-half months recovering from injury, it was only normal that a schedule that had the Senators playing five games in eight nights would wear on Karlsson. But if his stamina improves, look out.

Penguins will win if … They get better goaltending. It really is that simple. The Penguins proved during the first round that they can virtually score at will and that their fleet of forwards can present matchup nightmares for virtually any team in this tournament. Yet none of that will matter if the goaltending goes south like it did for a three-game stretch of the first round. As the competition becomes better, those meltdowns in goal will become more telling.

Senators will win if … Anderson maintains his dominant level of play and they are able to physically wear down the Penguins the way they did the Canadiens. Ottawa has developed a never die, us-against-the-world attitude and they thrive on people doubting them. The entire hockey world will doubt them against the Penguins, so the “pesky Sens” will need to use that to fuel them again.