Here's my hold up with taking Mariota at #2.....and QB in general. (leaving out trading back.....which is a great option)
1. Obviously Mettenberger doesn't appear to be a crazy superstar. So, until proven otherwise you want an upgrade. However, he did play just well enough that he can provide opportunity to be patient finding "the one."
2. If Philip Rivers is in play, then I would so much rather have him. A proven top 6-8 ranked QB who has played Whiz's system just a few yrs ago that sent him to the Pro-Bowl. And he has at least 4-5 yrs left of high level play......perhaps more. If the price isn't too steep, you gotta take that.
3. Mariota has all the character and physical tools, however his fit is very poor for the Titans. By all accounts, it's likely going to take him at least 1......if not 2-3 yrs to even learn a pro-style offense. And that's "IF" he does. There's a chance that he never will. His mobility can help mask some deficiencies at first, but do you want to rely on that? So, do you choose a better value in the draft......basically taking Williams, Cooper, or White? Basically taking a guy that would have a much sooner impact......someone that fills a giant need on the team, immediately........someone that who has a floor of the occasional pro-bowler, with ceilings sky high? Or, do you take a shot in the dark for a square peg QB, who is a bit of a project at a pro-style system, throw him to the wolves behind a struggling o-line/not so stellar receiving/no so stellar running game.......just because we need a QB?
I don't think I would. If trading back isn't an option.....and Winston is off the board......I'm going Williams. I will take BPA in the draft. Go into next yr with Mettenberger as the starter. Then really look to target a much better fitting in the 2016 draft when the QB class is expected to be much better overall and deeper. Then, whomever I choose, will jump in with a much improved overall team. And you have a veteran back-up in Mettenberger.