Think about....

Buffalo isn't going to retain Eichels salary. Eichel is get 10 Million for the next 6 years after the draft (I believe not positive about the years) In a Eichel Trade your giving up Top Prospect (Kakko or Kravstov) , this years 1st round pick and next years, plus a roster player (Chytil, Strome, Buch?), and maybe 1 more piece prospect most likely (Schneider, Skinner, Lindqvist, Miller, or Jones)

In a Tarasenko trade what you give up? my guess Probably Kakko? or a the rights to Buch? plus this years first round pick (Pick is going either way). Also every Gm in the NHL knows Tarasenko wants out so Blue return will be less, plus Blues are going to have to retain due to all the injuries in the past. His contract is up in 2 years after the draft