McCoy is just about the only reason the Eagles won the division 2 years ago and is the one who made that whole offense go. Alonso is good but let's not forget that he played behind what is probably the best DL in the league in Buffalo with Mario Williams, Kyle Williams, Marcell Dareus and Jerry Hughes.
This trade smacks of arrogance to me, I think Kelly is overconfident in his little bullshit college scheme that generally only works against bad to average defenses. I'd really love it if they traded 2 drafts for Mariota because I could very easily see a scenario where the Eagles kind of flounder after giving up all those picks and Kelly just packs up his stuff and goes back to be the highest paid coach in college.