Cutter Gauthier scored, and Lukas Dostal made 21 saves for the Ducks (33-24-3), who had won five straight and 12 of their past 14 (12-2-0), including eight in a row at Honda Center.
"We've been fortunate that we've come back and we've shown a lot of resiliency with the group, but you can't do that in every game," Anaheim forward Alex Killorn said. "It's just not going to work that way, so we've got to find a way to get some leads and have some better starts."
Makar gave the Avalanche a 1-0 lead at 11:33 of the first period. He came out from behind the Anaheim net to retrieve a loose puck and skated through the left circle before scoring with a wrist shot from the hash marks.
It's the fourth straight game the Ducks surrendered the first goal.
"Playing from behind is not traditionally winning hockey," Anaheim coach Joel Quenneville said. "You can’t expect to keep chasing a game."
Necas scored on Colorado’s first power play to extend it to 2-0 at 14:05 with a one-timer from the top of the left circle, his fifth goal in the past five games.
“A lot of these games, we've been able to come back, but against a team like that, can't spot them two goals. They're just too good," Killorn said. "After they scored those two, we fought back a little bit, but it just wasn't enough.”