PHILADELPHIA (AP) — Niklas Hjalmarsson picked a bad time for his roughest night in the playoffs. Until a late rally, the rest of the Chicago Blackhawks didn't fare a whole lot better.

The 23-year-old defenseman coughed up the puck twice in front of his net in the first period, and the opportunistic Philadelphia Flyers took advantage of both gaffes. That was enough to beat the Blackhawks 5-3 on Friday night, send them to their first true losing streak in months, and tie up the Stanley Cup finals after four games.

"It started bad with two bad plays there from me. It's obviously not good," Hjalmarsson said. "I just tried to forget about that first period and tried to do the best I could."

Hjalmarsson, in his first full NHL season, had been solid in the playoffs — putting up a goal and six assists along with a plus-9 rating in 19 games. But it all came crashing down on him amid the Flyers' Orange Crush.

Now the Blackhawks, who scored twice in the third period to make it close, will head back to Chicago, where they won the opening two games of the series. They will face pressure in Game 5 on Sunday and know they will have to return to Philadelphia for Game 6 on Wednesday.

The Blackhawks had been 7-1 in the playoffs on the road before getting to Philadelphia.

"I thought we were going to take at least one," Hjalmarsson said. "We planned to. We're close, but close is not good enough."

Except for dropping its final regular-season game and the playoff opener to Nashville, Chicago hadn't lost two straight since a three-game skid in late March.

"It's a good wake-up call for us," said forward Andrew Ladd, who played his first game of the series following an injury. "This team has done well when coming back from adversity."

The Blackhawks took a pair of offensive zone penalties in the first period — the first by Ladd just 36 seconds in.

"I got a little overaggressive there right off the hop, but it got me in the game and they did a good job killing it off," Ladd said.

They weren't so lucky the next time when Tomas Kopecky's high-sticking penalty at 4:30 set up Hjalmarsson's first dose of trouble. Chicago won the ensuing faceoff in its own zone, but Hjalmarsson had the puck swiped off his stick by Mike Richards, who put a quick backhander in only 5 seconds into the power play.

That was just the beginning.

Chicago appeared to gain control when Hjalmarsson corralled the puck on his stick, but when he attempted to clear the crease of danger, Hjalmarsson swept the puck right onto the stick of Flyers defenseman Matt Carle, who fired a shot past stunned goalie Antti Niemi.

While Hjalmarsson was the biggest culprit in the Blackhawks' second consecutive loss to the Flyers, he had plenty of company. Chicago showed a lack of discipline in taking several penalties in the offensive end. Only one produced a goal, but each helped the Flyers gain momentum and fire up the crowd.

"We shot ourselves in the foot with a few mental mistakes in the first period," defenseman Brent Sopel said. "There is nothing we can do it about it. It's over and done with and we have to worry about Game 5."

The Blackhawks' brightest moment until the end came in the closing stages of the first period when a slap shot by Patrick Sharp from the blue line clipped the stick of Flyers defenseman Braydon Coburn in front and caromed in to cut Chicago's deficit to 2-1 with 1:28 left.

All set to go into the intermission on a high note, another lack of focus proved costly again.

Sopel got caught chasing forward Scott Hartnell in Chicago's end, leaving room at the top of the zone, Hartnell fed the puck to Kimmo Timonen, who had plenty of time to find Claude Giroux wide open at the left post for a slam dunk goal. That restored the Flyers' two-goal lead.

Despite allowing only eight shots in the first period, Chicago trailed 3-1.

The Blackhawks still aren't getting the necessary production out of top forwards Jonathan Toews, Patrick Kane, and Dustin Byfuglien, who have combined for only one goal and four assists in the four games.

Kane assisted on Dave Bolland's 5-on-3 goal that made it 4-2 in the third period, That marked the Blackhawks' first power-play goal of the series in nine chances. Brian Campbell's goal with 4:10 remaining made it a one-goal game.

Chicago has also been burned while killing penalties. The Flyers have clicked on five of their 16 opportunities.

"We have to stay out of the box," Sopel said. "They have a great power play and we keep giving them opportunities to put them in, and they have done it so far."