I took an expected totals goals created (GC) by Spezza, Karlsson, & Ryan. Then factored in the values they would be replacing.
Again, I wasn't getting into trying to judge the difference in the rest of the lineup, because I believe it will be a wash. For example Spezza being there will stop Turris from playing 20 minutes a game. Any benefit Turris will gain from playing lesser competition will be negated by less TOI within a goal or two.
I just don't see enough offensive improvement to overcome what a Ottawa simply returning to a "fantastic" SV% would cause. A team .935% is ****ing insane, a full percent higher than the 2nd place team...put another way, over an entire season Anderson-Bishop-Lehner would have been ~25 goals against better than the 2nd best goaltending in the league had both faced a roughly league average shot total.
That's an incredible gap. The largest gap between 1st and 2nd place in team SV% in the previous 10 seasons was .005, and only twice was the gap larger than .003.
The Senators had a monstrous statistical anomoly of a season in net last year...kind of like the Blues the season before (.929).