The Sabres have been actively trying to trade Eichel for quite some time, but seem extremely greedy in their demands. Remember that the organization refused to let the number 9 go under the knife, because this kind of practice has never been done on a player in the NHL. However, this operation would greatly help the long-term health of the American.
The Sabres are probably afraid that Eichel's recovery time will affect negotiations with other teams. They want to get the moon in return for him, but it would be surprising if they end up getting it, as the 24-year-old should have a long recovery.