This was supposed to be Forsberg's home debut in his latest NHL comeback but the Avalanche announced Monday morning he was retiring after two games with the club because of his troublesome right foot.
Fans who expected to see the star were witness to Colorado's worst loss of the season.
"Tonight was completely unacceptable," center Paul Stastny said. "We should be ashamed of our performance."
Forsberg was disappointed he could not overcome his nagging foot problem.
"We can fly to the moon, we should be able to fix the foot," Forsberg said at a news conference Monday in Denver. "It's been a problem and not one we've be able to solve. But it's OK now. I'm happy with my career and move on from here."
The former NHL MVP signed a $1 million prorated deal last week to play the rest of the season for the team he helped lead to two Stanley Cup titles.
Forsberg played two road games but didn't record a point in more than 35 minutes of ice time.
His foot started bothering him again so the 37-year-old reached the decision Sunday to retire.
"I'm really happy that I got the chance with the Avalanche to come back here and try for the last time and put an end to it," said Forsberg, who will have his No. 21 sweater retired by the team at some point next season. "Knowing for fact, 100 percent sure, that I'm not going to play anymore.
"When I look back, I'm going to be feeling pretty good about my career."
Anton Babchuk, Alex Tanguay and Matt Stajan also scored and Miikka Kiprusoff had 17 saves for the Flames, who had five goals in the first period. Backup goalie Henrik Karlsson played the final 6:51 and made five saves.
"It's fun when you score goals like that," Moss said. "It's good mood a good feeling hopefeully we can keep it going."
Daniel Winnick scored for Colorado, which has lost eight in a row and 10 of 11. The Avalanche also lost center Matt Duchene to a hand injury late in the second period.
Colorado coach Joe Sacco said Duchene will be evaluated Tuesday.
The Avalanche allowed five goals on the Flames' first 13 shots and made three goaltender changes. Moss scored 18 seconds in and Babchuk scored at 5:57 to chase Peter Budaj.
Craig Anderson didn't fare much better, giving up goals to Iginla, Glencross and Jokinen in a span of 5:47.
"They were definitely flat, and you could see some reasons," said Iginla, who has 25 goals this season. "It was probably a pretty emotional day for them as players and their fans, and it's also trying to stop their streak and they come back home."
The Avalanche said Forsberg's retirement wasn't a factor in their play.
That was not the reason for what happened out there tonight," Sacco said.
Budaj was back in net to start the second period and gave up goals to Tanguay, Glencross and Iginla in the third and finished with 13 saves and five goals against.
Anderson gave up a goal in the final 10:44 and finished with 11 saves.
"It was one of the worst nights I've ever had," Budaj said. "This was like a nightmare because everyone was not ready. I don't think there was one positive thing in the game tonight."
Colorado's frustration boiled over at the end of the first when Philippe Dupuis kneed Jokinen and received a game misconduct. Jokinen lay on the ice before gingerly skating to the locker room.
Jokinen played in the second period but sat out the third with what Calgary said was a lower body injury. Winger Tim Jackman also left the game with a lower body injury after the second period.
Jokinen had four points in the first, the fourth time a Flames player has had four points in one period. The last one to do it before Monday was Al MacInnis against Edmonton on March 28, 1991. ... The Flames' five goals in the first were their most in one period since they did it against Chicago on Oct. 12, 2009. They lost that game 6-5. ... The nine goals were the most allowed by the Avalanche since the franchise moved to Denver in 1995.