Try this : identify your 9 keepers (with McDavid)
Then pretend you make the trade and do your keeper again.
What would you drop (and can you recoup with trade at the end of the year?)
It's a really good value but if I was an McDavid owner, I woudn't trade him now... Unless you are going for it this year... But I would ask a little bit more of him (try to land some draft picks). Make him "bleed" a little...