Anaheim Ducks coach Bruce Boudreau said he saw something in his team in the second period for the first time in the playoffs.

It wasn't good, either.

The Ducks allowed three goals in a 3:45 span in the middle period and lost 5-2 to Duncan Keith and the Chicago Blackhawks on Wednesday night, sending the Western Conference finals to a Game 7 back in Southern California.

"We lost our composure for the first time I thought in the playoffs," Boudreau said. "They scored the one goal. It was like, aah, what's going on? We started scrambling all over. They got the momentum. We lost our composure. That was the theme that I saw."

Patrick Maroon and Clayton Stoner scored for the Ducks, and Frederik Andersen made 18 saves. Anaheim was coming off a 5-4 overtime victory in Game 5 on Monday night.

"We came in and got outworked tonight," center Ryan Getzlaf said. "We've got to be better than that."

The Blackhawks' biggest stars stepped up at key moments in the game, led by another terrific all-around performance for Keith. Shaking off the Ducks' plan to wear down Chicago's top four defensemen, Keith had three assists and saved a goal in the third period.

"He's kind of a freak as far as his metabolism and conditioning level," coach Joel Quenneville said. "I think the more he plays, the more efficient, the more he gets going."

Andrew Shaw had two goals in the third, sending the Ducks to their first regulation loss of the playoffs. Brandon Saad, Marian Hossa and Patrick Kane also scored for Chicago, and Corey Crawford finished with 30 saves.

Next up for the NHL playoffs is a double dip of Game 7s to determine which teams will play for the Stanley Cup. The New York Rangers host the Tampa Bay Lightning in the East final on Friday night, and the Blackhawks and Ducks meet in Anaheim on Saturday night.

It is only the second time in the expansion era since the 1967-68 playoffs that each of the conference finals required a Game 7. The other time was in 2000, when the New Jersey Devils went on to beat the Dallas Stars for the NHL title.

"I think the finality of it is what stands out," Boudreau said. "I mean, one group is going to go home and one group's going to go play for the Stanley Cup."

The Ducks and Blackhawks each dropped a home Game 7 to Los Angeles last season. Anaheim blew a 3-2 series lead against the Kings in the second round, and the Blackhawks lost 5-4 in overtime on a deflected shot from Los Angeles defenseman Alec Martinez.

"That's why we play 82 games so we can go home for a Game 7 and take care of business," Anaheim center Ryan Kesler said. "I'm confident in this team and I'm confident we're going to give it our best shot and we're going to be successful."

Anaheim caught a break when Jakob Silfverberg brushed up against Crawford's glove on Stoner's first goal of the playoffs at 1:57 of the third, trimming Chicago's lead to 3-2. There was no call on the play and Crawford threw up his hands in exasperation after Stoner's big slap shot went into the net.

But Crawford quickly put the play behind him, hanging tough while the Ducks made a frantic push for the tying goal. He got some help from Keith when the two-time Norris Trophy winner swept a shot away from the goal line about 3 1/2 minutes into the period.

"It's unbelievable," Shaw said. "He's one of those athletes who digs down and finds that extra step."

Shaw finally got the Blackhawks some breathing room when he beat Andersen with a nifty backhander high into the net with 3:32 left. Andrew Desjardins made a nice hustle play to get the puck over to Shaw for his third playoff goal.

Shaw then added an empty-netter in the final minute as Chicago improved to 7-1 at home in the playoffs.

"I think we chased the game a little bit tonight and I think we let them dictate the second period," Kesler said. "They scored three quick ones. It's tough to come back from three goals. We gave it a shot there."

Keith picked up his first assist of the night when he made a long pass ahead to Kane, who touched it to a streaking Saad. The rugged forward then skated in and beat Andersen at 8:23 of the second, sending a charge through the crowd of 22,089.

The team with the first goal has won each of the first six games in the series.

Keith connected with Hossa for a pretty score at 10:41, patiently waiting while the winger got open for the other side of the net. He got his 14th assist of the playoffs when Kane made a dazzling move to get past Matt Beleskey and then managed to squeeze a shot past Andersen with 7:52 left in the second.

NOTES: Ducks D Simon Despres hurt his left leg in the third period, but returned to the game after a quick trip to the locker room. ... Blackhawks D Kimmo Timonen was inactive, and David Rundblad returned to the lineup for the first time since Chicago's 4-1 loss in Game 1 against the Ducks. ... F Emerson Etem got back in the lineup for the Ducks. F Tomas Fleischmann was inactive after he played 10:14 in Monday night's victory.

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Jay Cohen can be reached at http://www.twitter.com/jcohenap