Very interesting trade... I would probably pass though.
This trade has a very high ceiling, but also a low floor. Heyward could be big time... for year to come. But he could also be off to a big start [this year] and fade back into mediocrity just as fast. Nothing against heyward, I think he's a star, possible stud. Giving up Holliday is a pretty big commitment though.
I would at least wait a couple of months. If he's not interested in waiting, then what does that tell you: selling high.