Craig Anderson made 42 saves against his former team and the Senators won for the third time in four games. Ottawa remained four points behind Boston in the battle for the Northeast Division lead.
Daugavins broke a 1-1 tie 5:18 into the second period by tipping in a shot for his fourth goal of the season.
Bobby Butler, Daniel Alfredsson and Milan Michalek followed with goals that boosted Ottawa's lead to 5-1. Alfredsson's goal was the backbreaker, coming shorthanded with 5:04 to go in the middle period.
Anderson played for Florida during parts of three seasons before going to Colorado for the 2009-10 campaign.