Hayward was a big name , who even when he was supposed to be healthy seemed to not show up as a 30 million a year guy should , but shrink from the moment , mental issues .  This hurt the team and their play to watch him hide . im not subtracting the player we were suppose to have , utah Gordy .  He was about 1/2 what i thought at best.   
Teague is old , but a savy tuff minded veteran, who will like a solid smart coach like CBS .  Wanna tried and was a good soldier , but lacks the IQ and savy for playoff 1/2 court ball....Teague maybe as good as Kemba in a playoff game , if he can stay healthy. 
I liked Kanter alot , team first , great attitude was always AAA+ for the Celtics .  But , he seemed to be having advanced physical woes , that might require hip surgery or such and seemed to be dragging and moving slow .  His back , hips and knees maybe worn out . The years took their toll.  I think TT has more left in the tank and better health.   He can fill the lane and guard it from attacking bigs ,  something Theis is too small to handle .  So TT is an up grade over worn out celtics version of Kanter ,  TT has a bigs attitude as well and will look out for the smalls.