I doubt we do not qualify Sjostrom. But if for some bonehead reason we don't, we just gave away Montoya for nothing.
The problem is that if the Rangers give Sjöström a qualifying offer, they have to give him a raise--remember he was a first round pick. By not qualifying him, they can bring him back at a lower salary. But, of course, there's always the risk that he will choose to sign elsewhere in that situation.