Yes there is a big connection. As an Ottawa native and fan, Spezza and Karlsson stir the drink so to speak with Alfie getting older. When ottawas offense declined a few years ago it was because none of their dmen could get an outlet pass to streaking forwards. Meanwhile Spezza is the main playmaker (and scorer) once he has the puck.
None of the other players are creative offensively (maybe Turris but not consistent yet), and Michelak can score,but is injury prone.
If a couple prospects develop faster (Silver surfer, Zbad, and Stoner) then maybe they become less dependent on Spezza.
I think Karlsson would be a 50 pointer dman without Spezza, and vice versa Spezza a 70 pt C without Karlsson. Together it's another 15- 20 points each.
Rough estimate but I counted 33-35 of karlssons points last year that Spezza either scored or got an assist, and vice versa.