Guerin gets that success in professional sports, especially hockey, comes down to character. Fiala is a highly-talented player who does not have the highly-motivated character aspect -- at all. You see the same thing with, say, William Nylander. A guy who puts up points is certainly a terrific guy to have on your team. A guy who won't win puck battles, who takes bad penalties, who makes selfish turnovers... is just not worth what his market value says he is -- especially in the playoffs.
Now, it's a fair question whether losing Fiala will contribute in a negative or positive way to making the playoffs next season but Guerin obviously sees his mandate as building culture first and foremost.
I'll miss Fiala as much as I missed Havlat and I do think Guerin can get a solid return for him.