Tannehill is a very raw prospect that has tremendous upside and could move into the top five. He is athletic enough to make the throws outside of the pocket and move within the pocket when pressure comes.
He is very sensitive to pocket pressure. That sensitivity doesn't mean that he is afraid to get hit; it means that he knows when to tuck the ball, when to throw it and when rushers are closing in.
He has a good release and has raw arm strength. He shows a lot of guts running down field and doesn't cringe from hits. The same can be said about him in the pocket; he follows through on his throws even if he is going to get thumped.
The Browns could use an upgrade at QB, but Tannehill is not NFL ready. Granted that he comes from a run-first, pro-style offense, but he doesn't have the experience under his belt that you look for in a day one starter.
The Browns RT issues mean he could get hit more often than he should, which could hinder his growth. Tannehill doesn't keep his eyes downfield as well as Cam Newton did, and if he is going against the elite AFC North defenses, they could jump his short routes or just knock him out in that situation. We'll need to rely heavily on the run game and play action to be successful, and the Browns are not equipped for that.
I don't like him this high. If they could trade down and get him a little later in the draft after adding more pieces, I would be okay with this.
Also, not signing any big name players in FA really makes me think that they are going to have to build through the draft. That doesn't spell success for a rookie QB with no weapons—especially one that will need more coddling than most.
Also, the Browns have Colt McCoy who fans love. While McCoy is a decent starter, if the Browns give him weapons this year and he doesn't produce, fans may need to get ready for him to get the boot.
He is a game manager that may be a backup QB only. He could prove me wrong this year, and I hope he does. If he doesn't though it is either his job or Shurmur's—maybe both.