The Calgary Flames picked an in opportune time to let a late lead slip.

Calgary, the NHL's best team at protecting leads after two periods, blew a lead after 40 minutes for the first time in over six months, falling 5-4 to the Anaheim Ducks on Monday in Game 3 of their opening-round series.

The Flames are now one loss away from elimination because of it.

"We've been so good throughout the season at protecting leads," Flames coach Glen Gulutzan said. "But tonight, for whatever reason, we couldn't hold onto this one."

Calgary was 33-0-1 when leading after two periods in the regular season, good for a .971 winning percentage. The Flames had one overtime loss on Oct. 15 before going 33 straight wins when faced with that scenario.

That streak came to a crashing and crushing halt before a raucous sellout crowd at the Saddledome.

Leading 4-1 late in the second period, momentum started to turn as Anaheim's Shea Theodore scored with 49 seconds remaining in the second period.

Two more goals in the third tied it and Corey Perry's bank shot off of Calgary defenceman Michael Stone 90 seconds into overtime turned a jubilant night into one of heartbreak for the Flames and their fans.

"We've got to find a way to hammer that one down for sure," said captain Mark Giordano. "We got four goals, you've got to win the game. That's the bottom line."

Brian Elliott, who was shaky on a few of the goals, accepted his share of the blame. The five goals came on 27 shots, five fewer than what the Flames had directed on Anaheim's net.

"It's tough to swallow right now," said Elliott, who had only given up five goals once in the previous five months. "I have to own that. It's not an easy thing to do. The guys potted four goals and we should win a game like that."

'It came back to bite us'

Sitting back on their heels, Calgary was outshot 12-8 in the final 20 minutes, enabling the game to slip away.

"It's not the way we wanted to play the third period," said Stone, whose first goal of the series made it 3-1 early in the second. "We let them back in the game and it came back to bite us."

As fans quietly filed out of the Saddledome, it was just as silent in the Flame dressing room.

"It sucks," said a quiet Sean Monahan, who scored his third goal in as many games. "It's a 4-1 lead and you blow it and you go and lose in overtime.

The Flames talked post-game about regrouping and moving on. It's going to be very difficult climb.

Winning four straight to take the series would mean having to win twice at Anaheim's Honda Center, where they've lost 29 consecutive games.

The Flames have never come back to win a series in which they were down 2-0, let alone 3-0.

"It's going to be difficult tonight, you expect that," said Gulutzan. "We will get up in the morning and do our same routine to make sure we are ready for Game 4."

Game 4 goes Wednesday in Calgary.

"Put this one behind us and move onto the next one," said Stone. "One at a time."