Callahan and his agent must have realized before this rumor surfaced that lowering demands was the only way to stay. Maybe the Rangers are lowballing Callahan because they are ready to move in another direction.
If Stewart wasn't on the table (assuming he is), then it would be for the same reasons every other team is not offering the Rangers "more". You don't give away consistent performer with size, speed and fists, for a rental. Callahan is tough, is an awesome 3 on 5 defender. That's the kind of thing a contender would value.
But, what do I know? I think "heart and soul" is way overrated, to put it mildly. Or, do we believe that Hank straightening out his game, Nash lighting it up, and Staal getting better and better all the time is somehow related to Callahan returning to the lineup? I don't. Players these days are so savvy, if the average to way above average fan knew what went on in these guys heads, if they knew true insider stuff, the effect might be akin to a hippie finding out that aliens are real.
Stewart underperforms in St Louis? Wouldn't be the first power forward traded from Colorado who went into a funk. Way back in 96 Colorado traded Owen Nolan to the Sharks for Ozolinsh. Nolan went into a funk that lasted until his contract was set to run out. Then he had a career year. Maybe Stewart hates it in St. Louis. Especially considering where he was previously. That trade, if anybody remembers, brought out a furious response from Statsny's father. Imagine how Stewart must have felt.