If the Avalanche miss the playoffs and the Sens make the playoffs; The Sens have to give up their 2019 2nd and a 2018 3rd.

This deal works for both sides. Both Turris and Duchene are 1st line centers, and both are on the block for both sides IRL. You could say that the trade won't be beneficial for the Senators as they have gotten rid of a solid defenseman and a 1st line center for an arguably "overrated" center. Although, Both Turris and Ceci are going to need new contracts at the end of the season; Turris is going to want a steep upgrade from the current $3.5 million salary and Ceci might want at least 3 million. Which would leave some wiggle room for White and Stone's contracts at the end of the season. Remember that the Avs need an upgrade in defense as they have Bernier as their backup and Varlamov as their starter. It just works for both sides. The 2nd and 3rd is mainly because Sakic has a steep asking price for Duchene.

A necessary slight upgrade on the right side, seeing that the middle is stacked in Ottawa. Just a small swap.

Removal of a mostly useless player. Honestly, the trade is good on both sides as Claesson to play full minutes and the Kings get a 3rd line defenseman when they really need one.

Vegas gives up a reasonable 3rd line winger for two low value prospects. Ottawa does this deal since MacArthur is on LTIR.