When one player rises on the depth chart, another must fall. For the Broncos at running back, that meant third-round rookie Ronnie Hillman was sliding down the table when Knowshon Moreno ascended back to the No. 2 role behind Willis McGahee this week.

Lance Ball's drop from No. 2 to No. 3 was no surprise. Ball was long pegged for that role, which will entail occasional use as an outside receiver or second back flanking Manning in the shotgun, in addition to the myriad special-teams duties he will assume. As a jack-of-all-trades, Ball fits the job description of the third running back perfectly.

But with Hillman, the drop to No. 4 came in spite of leading the Broncos in rushing in the preseason -- despite playing just two games. If you're looking for a reason, look no further than everything that doesn't involve running and receiving.

That Hillman has endured some ups and downs as a blocker is no surprise to offensive coordinator Mike McCoy, who described pass protection as "the hardest part" of a rookie runner's work.

"Without a doubt, because you see so many different pressures and people coming from different angles and disguising things and hiding things," McCoy said. "A running back, you hand him the ball, he's going to run. But it's the protection that's a major difference, I would say."

Moreno, on the other hand, has flourished in that role, McCoy said.

"He's always been a pretty good blocker," McCoy said. "He's never been afraid to stick his nose in there and fit up someone who's coming through on a pressure."

Hillman still fits in the Broncos' long-term plans, but for now, he'll be given time to develop -- which could mean time on the sideline during game days, unless the Broncos choose to activate four running backs. They never activated more than three last season.

"I think (Hillman) is like every rookie on the football team. There's so much more that we're doing right now offensively than what he did in college, it's going to be a day-to-day basis with him. He's going to learn something new every day. There's going to be a different look, or we're going to add things from week to week in game plans.

"We're not slowing down for anybody now. So you're not just getting the generic looks any more; we're throwing a lot at you and he's going to learn and get better every day."

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