General Manager Pierre Lacroix announced that he had promoted assistant coach Tony Granato to serve as Hartley's replacement.
"We've been nine years working with the organization and we haven't done anything with emotion in the past, and this is not an emotional decision," Lacroix said. "You talk about timing, there's no good timing for making a decision like that. But I have this responsibility and I had to do it.
"It's not something you do overnight. The time, for me, was today to address the situation."
Hartley, 42, is the second-winningest coach in franchise history with a 193-109-48-9 record in four-plus seasons. But Colorado is just 10-8-9-4 in 2002-03 and is currently out of a playoff position.
"We are an organization with very, very high expectations," Lacroix said. "It's no different this year. It's obvious the team is not showing any emotion, the team is not doing the things they need to do in order to fulfill these expectations. It's nothing in particular, other than I am convinced it was the right time to make the call."
Winners of eight consecutive division titles, the Avalanche are fourth in the Northwest Division with 33 points. Only five Western Conference teams have surrendered more goals than the Avalanche (80), who won the Jennings Trophy last season after yielding an NHL-low and franchise-record 169 goals.
Colorado reached the conference finals in each of Hartley's first four seasons, winning the Stanley Cup in 2001. The Avalanche, however, squandered a three games to two lead in last season's conference finals and were routed by rival Detroit, 7-0, in the decisive seventh game.
Granato, 38, is a coaching neophyte. He ended a 13-year playing career following the 2000-01 campaign and spent last season as a broadcaster before joining Hartley's staff.
"If I wasn't ready, I wouldn't have said yes," Granato said. "Experience is no problem at all. I've been in this game a long time. I know what I can bring to this team and I'm looking forward to the challenge."
"Knowing what I know about Tony and the way's he been handling himself since August, it's obvious that he's got all the attributes and all the assets to do the job," Lacroix said.
Granato will make his coaching debut Thursday, when Colorado hosts the Edmonton Oilers.
Hartley was the third coaching casualty of the season -- all in the last three weeks. The San Jose Sharks fired Darryl Sutter on Dec. 1 and replaced him three days later with Ron Wilson. The Calgary Flames axed Greg Gilbert on Dec. 3 and still are looking for a successor while Al MacNeil serves on an interim basis.