The biggest is that No. 12 is simply too high a spot to select Locker.
Most player-personnel types I've spoken with say that the former University of Washington quarterback does not earn a first-round grade, let alone a top-15 designation. They point out that Locker's skills are extremely raw, and that he needs far more work than the two quarterbacks widely viewed as upper-tier, first-round picks -- Cam Newton and Blaine Gabbert -- as well as other prospects at the position.
They love Locker's arm strength, but are troubled by his considerable accuracy problems and the ill-advised risks he often takes because of his overconfidence in being able to power the ball between defenders. They love his athleticism, but cite consistently poor pocket awareness as a reason he doesn't avoid more sacks than he should.
All rookie quarterbacks are, to one degree or another, projects. But Locker looks to be one of the bigger and more challenging ones from this year's crop.
The Vikings' desperation for quarterback help -- and the fact that it might be a long time before the free-agent market opens -- could very well cause them to push a rookie, especially one selected 12th overall, into the lineup right away.
By all indications, Locker would be woefully unprepared for that.