Nashville moved closer to a playoff berth, jumping past Anaheim into the sixth-seeded position in the Western Conference chase.
Erat then scored on the power play with 7:08 to go in the third, giving Nashville a seemingly comfortable advantage. His goal, however, turned out to be the game-winner when Paul Stastny and David Jones scored for Colorado.
The goal by Jones came with 1:02 left in regulation.
Pekka Rinne made 27 saves to get the win, Nashville's seventh in eight games.
Brian Elliott gave up the three Nashville goals on 34 shots. The Avalanche, who have been eliminated from playoff contention, lost their fourth straight.