"We played pretty consistent through the whole game," said Sexton, whose team had 43 shots on goal.
Trailing by two and with time winding down, the Ducks didn't rattle or get flustered.
Instead, they stuck to the game plan of putting shots on Anderson and crashing the net.
That allowed them to crash what was turning into a victory party by the Avalanche.
"We didn't change our game plan much and went out and found a way to get a goal," Ducks coach Randy Carlyle said. "We got another one."
And finally the win.
Jonas Hiller had 15 saves to bump his winning streak to four games.
Brandon Yip scored his first NHL goal for Colorado, while Paul Stastny added another.
The Avalanche appeared to be cruising toward the win, when the wheels suddenly flew off.
Niedermayer scored his fourth goal of the season with just over 7 minutes remaining. Anderson was none too pleased, though, as he felt Bobby Ryan interfered with him in the goal crease.
However, the play never went to review.
That upset the Avalanche, who thought it should've been goaltender interference.
"Andy's laying on his back, how's he supposed to make a save?" defenseman Kyle Quincey said. "What's considered goaltender interference if that's not?"
With 4:55 remaining, Sexton tied the game when he slapped in a pass from Saku Koivu. The Pepsi Center crowd suddenly went quiet.
The game seemed headed for overtime, but Getzlaf gobbled up a loose puck and knocked it by a sprawled-out Anderson to complete the stunning rally.
"When you're down 2-0 with 8 minutes left, you think things are almost wrapped up," said Getzlaf, who scored a goal for the fourth straight game. "It's a situation where we battled pretty hard and got a few bounces and were able to get back on the board."
Despite the late-game collapse, the Avalanche head into the Christmas break leading the Northwest Division.
But this wasn't exactly the way they wanted to go into the break.
"You have to let them go," Scott Hannan said. "We are still in first place and we know we are a great hockey team. ... You know it is tough when you play 82 games, those are going to happen. You don't want them to happen. You have to take away what you can from it and learn from it."
The Ducks have one more game before the holiday hiatus, traveling to Phoenix on Wednesday night.
Anaheim kept the pressure on in the second period, outshooting Colorado 14-4. But the Ducks couldn't get anything past Anderson. It certainly wasn't from a lack of point-blank opportunities. Anderson blocked a shot by Corey Perry with his chest, then later turned back James Wisniewski's slap shot from the right side with less than a second left in the period.
All the pressure eventually paid off.
"The first goal was huge for us because it kind of broke the ice for us and we were able to get a few more right after that," Sexton said. "They had some big goals, but we carried the play."
The Avalanche jumped out to an early 1-0 lead in the opening period when Yip took a pass from Matt Hendricks and lined it by Hiller. Yip becomes the latest member of Colorado's youth movement. So far this season, the Avalanche have had six different players make their debut.
This was Yip's third career game after being recalled from Lake Erie of the AHL on Friday.
Colorado F Marek Svatos missed his fifth game with a groin injury. ... First-year Avs coach Joe Sacco said that D Ruslan Salei will be sidelined indefinitely after recently undergoing back surgery. ... Sacco was a member of Anaheim during the team's inaugural season in 1993-94. .. Anaheim has won five straight over Colorado.
Copyright by STATS LLC and The Associated Press
Arena: Pepsi Center Location: Denver, Colorado
Referees: Rob Martell, Mike Leggo Linesmen: Jay Sharrers, Brad Lazarowich
Attendance: 12,171 (67.6% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Brandon Yip (1)
Assists: Matt Hendricks, Brett Clark
No scoring this period
Paul Stastny (9)
Assists: John-Michael Liles, Wojtek Wolski
Scott Niedermayer (4)
Assists: Corey Perry, Ryan Getzlaf
Dan Sexton (5)
Assists: Saku Koivu, Matt Beleskey
Ryan Getzlaf (10)
Assists: Corey Perry, Bobby Ryan