ENGLEWOOD, Colo. -- Close your eyes and imagine the sensation of being a rookie and stepping onto the practice fields of the very NFL franchise you cheered for - with heart racing and eyes glowing like the aurora borealis - as a seven year old on Sunday afternoons.

Now, take a deep breath and envision lining up in the backfield next to a quarterback wearing a ubiquitous number 18 on his jersey with the name Manning on the back -- an image that stands as pronounced as the Empire State Building when it comes symbols of the NFL.

For Broncos rookie running back Montee Ball, that dream is now very much a reality.

"At first, I was star struck," Ball said after Monday's OTA practice referring to playing alongside Peyton Manning. "I'm not going to lie. I grew up watching him. But now, I don't want to say he's (just) another quarterback, but I'm looking at him as someone I'm most definitely learning from."

And while expectations for his contributions to the team are high, Ball is growing more and more comfortable with that reality each passing day.

"It's funny because today I came in feeling extremely comfortable," Ball said. "The jitters are gone and now I'm ready to play. I feel like I sort of showcased that today in practice. I knew all of my assignments and I didn't look like I was a chicken with his head cut off in the backfield."

With veteran Willis McGahee absent from OTAs and Knowshon Moreno recovering from injury, Ball has received ample time practicing with the offense over the past few weeks.

The reps have helped Ball overcome the initial nervousness that accompanies being thrust into an NFL offense for the first time.

"I was nervous," Ball said. "Just thinking about messing up, creating my own fear is what I was doing. Mostly, it's just making sure I know all the audibles and changes that are going to happen with Peyton at the line of scrimmage."

"He's better than me, because I had the jitters all year, every time I got in," said Ronnie Hillman, who has split time with Ball in the backfield. "He adapted a lot faster than me. But, I mean, you get to a level of comfort and familiarity when you're actually getting reps with the ones." In order to develop that comfort zone and better understand his role in the offense, the Broncos' second-round pick in the 2013 NFL Draft has seized every opportunity to pick Manning's brain with questions during - and after - the Broncos' practice sessions.

"It's been big," Ball said, noting that working with Manning requires an understanding of every player's role on a given play. "The biggest adjustment from (Manning) is all the audibles that he makes because he's capable of - as we all know - changing the play at the line of scrimmage. You've got to know not only what the running back's route is on a play, if he's spread out and empty on a play, he can change the route from the first routes to the second routes." In learning the complex details of an NFL playbook and handling the demands of playing alongside Manning, there's been no room for shyness.

"(I ask Manning) a lot of questions," Ball said. "That's kind of what he told me at first, to ask questions. What he told me is that if you don't, then we expect that you know it, so for me, I'm just firing off a ton of questions right now."

And although the learning curve has been undeniably challenging, Ball has stepped up and exceeded his own expectations.

"First, obviously, it was rough," Ball said. "Different terminology and everything, kind of like learning a different language. But I'm doing a lot better than I expected. The playbook's coming along really well."

Now, the nerves are subsiding and Ball is settling into his role as a contributor to the offense.

"I (felt like I was dreaming) a while ago, but now you can't really do that because it's all about the playbook and stuff," he said. "I'm still most definitely grateful for the opportunity that I've been given, but now it's time to play football."