A sluggish start and penalty woes sunk the Flames in Edmonton on Monday night.
Calgary dropped a 5-2 decision to the Oilers at Rogers Place, allowing three powerplay goals and being outshot 17-5 in the opening stanza.
The Flames ended up taking 12 penalties in the setback while the Oilers were tagged with five.
"I thought first period, we weren't very good at all," assistant coach Dave Cameron said afterwards. "We were working hard but we didn't have any real structure or process to it.
Cameron liked how his club rebounded in the second stanza, putting more pressure on the Oilers' defence corps and establishing a presence in the offensive zone.
"Second period, we were real good. We competed more. We did a better job of managing the puck. We were harder. We made the simple plays.
"In the third period, we really didn't give ourselves a chance," Cameron noted, acknowledging the 5-0 deficit the team found themselves trying to claw back from after 40:00.
In the opening minutes, Caleb Jones put a shot on net from above the hashmarks, which was redirected by Iiro Pakarinen. Eddie Lack made the initial stop but Mark Letestu was waiting on the doorstop and smacked the rebound over the netminder's pad.
Just over three minutes later, a rebound off of Patrick Maroon's shot led to a Ryan Strome powerplay goal. The forward stormed towards the side of the net and snapped the puck into the open net to give his team a 2-0 lead at 5:20.
Emile Poirier nearly got the Flames on the board late in the period but was denied by the post. Sam Bennett, taking a pass from Poirier after steaming into the offensive zone, cut through the slot and deked around a defenceman before making a quick pass to his winger. Poirier got his stick on it but put the shot wide, bouncing off the far post.
"I didn't even want to say anything to him, he knew," Bennett said of the play. "It happens to everyone. You just shake it off. I'm sure if he gets another chance like that, he's going to bury it."
Ryan Nugent-Hopkins added the Oilers' third goal at 14:50. Grabbing the puck behind the net, he looped around and put a shot on net. In the battle for the rebound, the puck bounced off of a defender and past Lack.
As scheduled, the Flames swapped goaltenders at the midway point in the second period and David Rittich took over in net. Lack ended his stint with 20 saves on 23 shots.
"I felt like I had a couple of bad bounces," Lack said. "But it's pre-season for everyone - we're just trying to work out the little kinks and stuff. Get used to each other and stuff like that.
"I felt that I got better and better as the game went on."
Letestu made it 4-0 with a powerplay goal at 5:20 of the third period, rifling a shot over Rittich's glove from close range.
On a five-on-three power play, Strome scored the Oilers fifth goal. Connor McDavid put the puck on net and in the midst of a scramble in front of Rittich, Strome whacked it in the net.
Bartkowski broke the Oilers' shutout bid when he pounced on a bouncing puck in front of Edmonton goaltender Edward Pasquale, slipping a shot short side. The goal, assisted on by Michael Stone, came at 16:06.
Hunter Shinkaruk gave the Flames their second goal of the night when he was able to tip Stone's slap pass while Calgary was on the powerplay.
Rittich ended the night with seven saves on nine shots in 27:50 of ice time.
The Flames also suffered a setback in Calgary on Monday, falling 5-4. Sean Monahan, Dougie Hamilton and TJ Brodie, and Mark Jankowski scored in that loss.
The Flames are back in action on Wednesday when they host the Vancouver Canucks at the Scotiabank Saddledome at 7:00 p.m. MT.