I don't know why so called knowledgable fans are worried about players leaving as UFAs "for nothing".
There are about 90 UFA every year, they all don't get traded. Contending teams, even playoff teams aren't sellers at TDL they are buyers.
In absurd that the Leafs would trade Gardiner for futures just because he is leaving as UFA. If Gardiner makes the Leafs better in 2018/19, he is certainly staying a Leaf.
Looking the Leafs cap for 2019/20, I doubt if there is cap room for Gardiner anyway. If the Leafs have six expensive forwards....Marleau, Kadri, Tavares Matthews, Nylander and Marner, they will will be depending on some cheaper, ELC Dmen.