ENGLEWOOD, Colo. (AP) — 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 and a win at Oakland (4-11) on Sunday 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.

“Growing up, where I’m from, people aren’t shy to tell you to your face, ‘You’re not going to make it. You’re a Mexican, for one thing. There’s not many Mexicans that play in the league anyways. You’re not smart enough. If you go to college, you’re going to have to go to a juco first and then go to college if you get an opportunity,'” Ramirez said. “I don’t know, it’s just some dumb stuff people were always saying, trying to put me down for whatever reason it might be. But you’ve just got to put all that to the side.”

Ramirez started 11 games at right guard for Denver last year, but free agency was barely 20 minutes old when he got a call from his old college teammate, Louis Vasquez, informing him he’d just signed a four-year, $23.5 million deal with the Broncos to play right guard.

“I was shocked, but at the same time I was excited because Louie and I got a bond that’s like brothers, so I was happy for him,” Ramirez said. “And then my mindset was I’ve just got to fight for a job.”

The Broncos had a plan in mind for Ramirez.

When Manning began the second chapter of his career in Denver following the series of neck surgeries that affected his famed right arm, he rebuilt his throwing motion from the ground up.

No longer does he rely as much on his arm strength so much as he does on proper mechanics, using more of his hips and torso to direct his passes and generate speed. So, it’s imperative that he has room to step into his throws.

That means, the Broncos needed more height and beef in the middle of their line, and they got it with Vasquez (6-foot-5, 335 pounds) and Zane Beadles (6-4, 305) at guard and Ramirez (6-3, 320) at center.

“That’s helped us become a little more powerful on the run and a little stouter on the pass,” Fox said. “So, those are areas you try to get better at physically. And then mentally is the thing that Manny’s done a great job with.

“He’s got a quarterback behind him that’s a pretty demanding guy and changes and does things on the fly, so you’ve got to be a sharp guy and you’ve got to earn his trust and he has and done an excellent job.”

BY ARNIE STAPLETON, AP Pro Football Writer

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