PITTSBURGH - One game, and the Pittsburgh Penguins already know this. Nothing comes easy for a defending champion, not even the playoff series opener against a seemingly overmatched opponent.
Erik Karlsson and Chris Kelly scored on power plays in the second period and the Ottawa Senators ignored their underdog tag and the Penguins' recent playoff success, surprising the Stanley Cup champions with a 5-4 victory in Game 1 of the Eastern Conference first-round series Wednesday night.
''Nobody's picking us to win the series,'' Ottawa forward Jason Spezza said.
Evgeni Malkin scored twice following penalties on Peter Regin, the first barely 3 minutes into the game, but the fourth-seeded Penguins looked mostly flat and uninspired for long periods in beginning their bid to become the NHL's first repeat champion since Detroit in 1998.
''We can't hang our heads and just say something (like) 'We didn't execute,''' forward Alexei Ponikarovsky said. ''We just have to do a better job. We've got to work and win the rest of them.''
Sidney Crosby, who piled up 15 points in his final five regular-season games, had three assists but was held without a shot until getting two in the third period. Ottawa constantly matched shutdown defensemen Anton Volchenkov and Chris Phillips against the Crosby line.
With their star so tightly covered, the Penguins - seemingly unsettled by Ottawa's defensive pressure - were held to a single shot during a stretch lasting 21 minutes, 53 seconds following Malkin's first goal.
The Senators, one of the biggest underdogs of the first-round qualifiers, went from being down a goal to being up 3-1 during that period as Regin, Chris Neil and Kelly scored - quieting a standing room crowd of 17,132 that clearly arrived expecting another long playoff run by the home team.
''For sure we'd like to get to their d-men and have some speed through the neutral zone, but that starts in other places, too, and we have got to get there,'' Crosby said.
Goalie Brian Elliott gave up four goals on 21 shots in his playoff debut, but made several big stops on Ponikarovsky and Malkin in the second period as the Penguins pressed to tie it following Malkin's second goal, at 10:22.
Instead, the 19-year-old Karlsson restored Ottawa's two-goal lead less than 3 minutes later, collecting a rebound of a shot from the left point by Matt Cullen that rebounded off Mike Fisher in front and wristing it into a wide-open corner of the net to make it 4-2.
No coincidence, the Senators said, that rookies Karlsson and Regin scored in their playoff debuts.
''They just feed off one another, if one scores, the other one's got to score to match,'' Neil said. ''They room together, they're inseparable. We call them the twins.''
On this night, they were twice the trouble for Pittsburgh.
''They (the Senators) made it very difficult, and their forwards were coming back hard (on defense),'' Penguins coach Dan Bylsma said. ''They had five men around the net and made it tough to get to the net.''
The fifth-seeded Senators also got a fortuitous bounce on Kelly's goal at 1:20 of the second that put them up 3-1. Chris Campoli was attempting to wrap the puck around the boards, but it took an odd deflection directly to Kelly close to the net with no defender near him. Kelly also had two assists.
''That bounce they got on that third goal ended up being the difference,'' Crosby said.
Pittsburgh made several more pushes, with Craig Adams getting a goal at 5:16 of the third after playing all 82 regular-season games without scoring. He scored three goals during last season's playoffs.
Again, the Senators answered as former Penguins agitator Jarkko Ruutu accepted Neil's giveback pass to beat Marc-Andre Fleury on a wrist shot at 9:40 of the third. Ruutu began the rush by controlling the puck along the boards and feeding it up ice. Fleury faced 26 shots during a shaky performance.
''I think there's a couple (of goals) he's going to be thinking about, is going to want back. He knows he has to be a lot better to give us a chance,'' Bylsma said.
Alex Goligoski cut it to one goal again by scoring with 2:14 remaining, but the Penguins couldn't tie it even as their white shirt-wearing fans stood, chanting, ''Let's Go, Pens!'' for most of the final 2 minutes.
The Penguins won seven of eight playoff rounds during the previous two seasons, losing only to Detroit in the 2008 finals, but this time they almost seemed to relax after Malkin scored off Sergei Gonchar's pass on their first power play of the postseason. The goal came almost too easy and, rather than building on the early momentum, Pittsburgh allowed it to slip away and Ottawa tied it on Regin's goal at 8:45 off a long rebound.
''I think we can to try to build off this,'' Spezza said. ''If we focus on the short-term and we're not looking too far ahead, we can slowly creep up on them.''
Game notes: Elliott is 3-0 in Mellon Arena. ... Crosby has two goals in 17 regular-season games against Ottawa, the fewest he has scored against an Eastern Conference opponent. ... The team that won Game 1 won both Senators-Penguins series in 2007 and 2008. The teams split, with Ottawa winning in five in '07 and Pittsburgh sweeping the following year. ... Five of the last 10 Stanley Cup winners were gone by the end of the first round or did not make the playoffs. ... The Penguins were 2-2 in Game 1s last spring. They came back to beat Washington in the second round and Detroit in the finals. ... Pittsburgh had won its last five home playoff games. ... Ottawa was 2 of 3 on the power play after ranking No. 20 during the season, while Pittsburgh - ranked 19th - was 2 of 5.