What makes a first-round left tackle bust?

[Rain Man]

You take a guy like Jason Smith. Obviously he's been a disappointment to the Rams, but why?

When you look at an offensive tackle, you measure him, and that's pretty obviously objective. You can watch a ton of game tape on him to see how he plays in real-life situations. You can time how fast he gets into pass protection and how agile he is. Maybe it's harder to measure whether he can react to audibles, but really, if he's got elite measurables it seems like even if he screws that up he can get in someone's way.

So why is Jason Smith a bust? He was deemed an ultra-safe pick. What is he not doing, and was there some way it could have been measured? And not just him, but also Robert Gallery, Kwame Harris, Trezelle Jenkins (sigh), Mike Williams, Kenyatta Walker, Stockar McDougle, and so on.

Or for that matter, just stick to Jason and Gallery since they were ultra-high picks. Trezelle was known to be a project.

It just seems like there are relatively few variables that are critical for an offensive lineman, and that all of them should be identified and measured by now. These are, after all, multimillion dollar investments.