Manny Ramirez has arguably the toughest job in pro football. As Peyton Manning's center, he literally works under the most demanding quarterback in the NFL.

Not only that, but before this season, the seventh-year journeyman from Texas Tech hadn't played a full year at center since his junior year at Willowridge High School in Houston — way back in 2000.

With Ramirez as its anchor, the Broncos' offensive line has allowed the fewest sacks in the NFL (17), giving Manning time to throw his record 51 TD passes and plowing the way for Knowshon Moreno to top 1,000 yards rushing for the first time.

The Broncos (12-3) are 28 points shy of becoming the first 600-point team in history. A win Sunday against the Oakland Raiders (4-11) will secure home-field advantage throughout the AFC playoffs.

"Manny's been awesome," Manning said after a Christmas afternoon practice in pads. "That is no easy task to go from guard to center, especially in a sophisticated, fast-moving, always-changing offense. I think it would be one thing if you knew what play was going to be called and you had 40 seconds to process it. But we call one play and change it to the next with five seconds on the play clock and when we change a play, Manny has to make his own calls and he has just gotten better each week."

He's got the brawn and backbone to match the brains, too, Manning said.

"I know he has played through a lot of injuries. It speaks to his toughness," Manning said. "He is one of the strongest guys on our team, so it's very impressive. I'm not sure people (appreciate it). I think people in this building understand with the sophistication of our offense just how difficult his job is and he's just been outstanding."

Ramirez is an unlikely fulcrum for this historic offense, spending all season casting aside doubters and defensive linemen alike.

"This summer, I'm hearing all kind of grief about Manny can't do this, Manny can't do that," offensive line coach Dave Magazu said. "Well, I think Manny's proven all those people wrong."

Coach John Fox laughs now that nobody seemed to believe him when he kept saying in the offseason that Ramirez was his starting center and that he wasn't just keeping the position warm for J.D. Walton or Dan Koppen or Ryan Lilja or Steve Vallos or even Chris Kuper.

Ramirez, whose claim to fame before this season was bench-pressing a school-record 550 pounds in college, didn't listen to the skeptics but he couldn't help but hear them, either.

"Truthfully, and unfortunately, that's been my entire life," Ramirez said. "You know, even when I was playing in middle school and high school, I've always had doubters, and that's fine. That's always been motivation for me."

He's been proving people wrong since he first starting playing football.