ENGLEWOOD, Colo. -- This is what Peyton Manning has been working for.

Sunday night, the four-time NFL MVP will run through the tunnel at Sports Authority Field at Mile High for his first meaningful football game since Jan 8, 2011.

After working his way back from neck surgeries that caused him to miss the entire 2011 season, his first snap against the Pittsburgh Steelers will mark a significant milestone for the 15th-year quarterback.

But he's not ready to talk about that just yet. There are still two days of practice left this week.

"I'm looking forward to using these next two days," Manning said. "(Pittsburgh) gives you plenty of things to prepare for and study, so I think having a good Wednesday, and Thursday, and Friday practices are important. I thought we got off to a good start today. We need to finish the rest of the week."

That type of response came as no surprise to Head Coach John Fox, who said Manning has earned a reputation as a tireless worker.

"He's a consummate pro, I don't think there's any question about that," Fox said. "To see it firsthand right here in this building for his teammates, for the coaching staff -- whether it's the assistant coaching staff or the head coach -- it's pretty remarkable. Preparation is very critical in this profession, so he definitely goes about that as well as anybody I've seen."

But even if Sunday is too far away to predict whether or not he will "get butterflies," Manning did hint at what getting back on the field will mean.

"I know how hard I've worked to get back to this position, how much time I've put in to rehabbing, how much time I continue to put in, how hard I've worked to try to get comfortable in this system," he said. "That's really all that I know that I can do. I'm going to play as hard as I possibly can."

That's something Pittsburgh Head Coach Mike Tomlin said he doesn't doubt.

After watching Manning in the preseason -- particularly his final effort in which he gave the Broncos a 17-0 lead against the San Francisco 49ers -- Tomlin said Wednesday that "he looked like Peyton."

"This guy is Peyton Manning, and guys like him earn their reputations with their play, usually rising up in significant moments," he said. "Obviously this is a significant one for him, and we're expecting his very best."

Opening day, Manning said, is "as close to a playoff atmosphere as you can get in the regular season." Playing at home against a playoff-caliber team under the lights on Sunday Night Football only add to the electricity.

So are Manning and the Broncos ready for the first test of the 2012 season?

"Well," Manning said, "we'll find out."

"We're looking forward to it," linebacker Joe Mays added. "You couldn't start with a better game than the Steelers."