The second-year defenseman scored with 2 seconds remaining in overtime to give the New York Rangers a 3-2 victory over the Flames on Thursday night.
"Danny's a smart player, I know he's just putting it anywhere where it's not going to get blocked and it was fortunate that it kicked off the boards there," said McDonagh, who has two goals this season after scoring once in 40 games as a rookie last season. "We were talking about how the boards could be used to our advantage and it did there."
"It's a great experience for him because there has been some struggles with his play but he stays with it," New York coach John Tortorella said. "As we go through here, some of those guys that are in spots that they didn't expect to be in, it's going to help our team in the long run."
Marian Gaborik and former Flame Brandon Prust also scored for New York (2-1-2). The Rangers have won the first two games of their four-game trip through Western Canada. They play in Edmonton on Saturday night.
Brad Richards had an assist and has points in each of his first five games as a Ranger.
The Flames are 1-0-1 on their season-high, six-game homestand.
"It's tough to lose that game because we've talked about playing a certain style and getting more consistent and we were that tonight," Iginla said. "Guys played hard and it's the way we want to play."
After a four-goal first period, both teams were blanked over the final 45 minutes.
Flames coach Brent Sutter, staying true to his commitment to lessen Miikka Kiprusoff's workload this season, went with Karlsson in net.
In his second start of the season, the 6-foot-6 Swede made 26 saves.
"It's disappointing, but I think the guys played really good in front of me," Karlsson said. "It would have been fun to have a shot at the shootout and maybe win there but things happen."
In the third period with the Rangers pressuring around the Flames' net, Karlsson thwarted Prust from the side of the net after he was set up by Brian Boyle.
Karlsson was especially sharp in overtime, making five stops before the winner by McDonagh.
Henrik Lundqvist, coming off a 40-shot shutout in Vancouver in his last start, made 33 saves for New York. His best stop came on a first period rebound when he denied Tom Kostopoulos of the go-ahead goal, stretching across the crease to get his arm on the dangerous shot from the slot.
Lundqvist also turned in back-to-back saves with the game tied in the third, After stopping Jay Bouwmeester's dangerous drive from the wing, the goalie jabbed out his pad to deny Curtis Glencross on the rebound.
Lundqvist admitted he thought the game was going to go into a shootout.
"I was getting ready for it, so I was really happy to see the puck go in because they have some skilled guys to send out for a shootout," Lundqvist said.
Calgary LW Rene Bourque played in his 400th career game. ... Lundqvist was making his 36th consecutive start for New York, including four playoff games. His last night off was Feb. 11, 2011.