Here's my two cents on Sanchez versus Tannehille:
They're not a good comparison. They're not similar players. I'm not even talking about which will be better than the other, etc. I'm talking about style/story based comparison, it just doesn't fit.
Mark Sanchez was a prospect that, when you really looked at it, only had barely above average physical weapons for the position. We're talking things like height, build, foot speed, arm strength, release speed, accuracy, handling of pressure, power, etc. These are the more TANGIBLE tools a quarterback has to work with and Sanchez' package of physical tools was really only average to above average. He's only 6'2", the arm strength is pretty good but nothing to write home about. The accuracy was never special. His mechanics and release speed were not necessarily super quick. He does not have foot speed going especially in his favor nor was he uncanny at making big plays happen off pressure. His physical build and strength are not really a weapon.
What made Sanchez the story he was, was the INTANGIBLES. He's a winner, he's a leader, he knows how to operate an offense, he's mentally strong, great in the crunch, etc. All those intangible things that can only be indirectly observed or measured through things like wins or stats, he was supposed to have that stuff coming out his ears. Steve Young boldly declares that if all the quarterbacks in the Draft were on a bus together, Mark Sanchez would be the driver of that bus. He states that the only reason Sanchez isn't the top quarterback in the Draft is because scouts don't know what to look for in quarterbacks and they're always falling in love with tangibles and not really looking at what makes a quarterback successful.
Forget what Sanchez has since become. We're talking about what he WAS when he came out. I personally didn't buy his story, but that's irrelevant.
Prospect Mark Sanchez = Great Intangibles + Average Tangibles
Fast forward to Ryan Tannehill. We don't know what Ryan Tannehill WILL become. He could become as opposeite his Prospect status as Sanchez is opposite to his own. Who knows. But one thing that is widely agreed upon right now is that Ryan Tannehill has a boat load of TANGIBLES, but questionable/average INTANGIBLES. Look at his tangibles. He's 6'4" and around 225 lbs, probably 230 lbs at the start of the season. Pretty much ideal build. Taller and scouts start wondering how mobile you are. Shorter and scouts start getting nervous about batted passes and how well you see the field from inside the pocket. His arm strength is a weapon, really rockets in some passes especially comebacks off opposite hash at the college level (wider hash marks = even greater distance) which is kind of rare. Has an uncanny ability to make big plays off pressure, really accurate throwing the football on the run. Quickest release in the Draft, among those I timed. Has 4.5 speed and used to be his team's leading wide receiver, knows how to run with the ball in his hands. We're talking about a guy with a ton of physical, tangible tools and weapons at his disposal.
On the other hand, he's supposed to be a guy that has average or questionable intangibles. He's smart but that doesn't mean he's got great intangibles. Nobody that meets or interviews with him is coming away bragging about he's the driver of whatever bus he's riding on, etc. Regardless of how much that matters, if at all, it's true if you're being honest with yourself. He doesn't come off super mature like Luck, Weeden or Russell Wilson. He lost 6 games in 2011 and gets killed for it by evaluators and media. When you look closely to weed out the bull sh-t, he was about 50/50 at best in those really clutch, high pressure, do-or-die situations. He's not by any means a BAD character, nor is he a weak person, nor would I say he lacks confidence. "Average" does not = bad. Just saying the story right now is one of a guy with "average" intangibles. In other words:
Prospect Mark Sanchez = Great Intangibles + Average Tangibles
Prospct Ryan Tannehill = Average Intangibles + Great Tangibles
Total diametric opposites.
The better comparison for Tannehill is Jake Locker. Even though Locker was a four year starter Locker came out raw as an onion. While Tannehill is not nearly as raw in his mechanics, there are still some aspects of his game where his lack of starts really shows. Locker also boasted 4.5 speed. Both quarterbacks were beset by losses due in large part to bad teams around them. In Tannehill's case, his defense couldn't stop anyone. Both players have this uncanny ability and knack for making big and accurate throws, big plays on the run and when pressured.
That said, I think Ryan Tannehill is a much better prospect than Jake Locker. Much more accurate, much quicker learner.