It's not that Julius Thomas cannot. It's that he knows not.

On the field, in the moment, the Broncos tight end sees maybe five separate things once a play develops and acts accordingly.

On the sideline, Denver tight ends coach Clancy Barone sees perhaps eight separate things.

In many games, Thomas will run back to the sideline after a play and be met with a question from Barone. "Did you see that?" the coach will ask, referring to a block Thomas should have made or to a player who escaped his assignment.

"Not at all," Thomas said. "I didn't see it at all. Now I look at it, and I see it from a different perspective, and I'm like 'duh.' "

Thomas has had a breakout season as Denver's starting tight end, with eight touchdown receptions and 422 yards receiving. Two months ago, he was too often mistaken for the explosive offense's other Thomas — Demaryius. Not anymore.

What fans may not know is that Julius Thomas is struggling as a blocker.

Granted, being an NFL tight end in 2013 is vastly different than it was 15 years ago. Barone said he hasn't had a player at the position who put up receiving numbers as Thomas has, and could block exceptionally well, since he coached Atlanta's Alge Crumpler nearly 10 years ago. Tight ends no longer are 275-pound blocking behemoths. They're receivers who happen to block too. Even if blocking is somewhat an afterthought, it's still a requirement.

When he was put in as a tight end at Portland State during his one season of college football, Thomas was hesitant. He wanted to be a receiver. Receivers are not required to block much, and as a college basketball player, the skills involved in blocking were utterly foreign to him. Still, a tight end he became, and if receiving came naturally, blocking did not.