That said, he's glad to have a backup stepping in who's as accomplished as Dan Koppen, who spent his first nine seasons in New England snapping for another great quarterback.
While everybody else was focused on his arm strength upon his arrival in Denver seven months ago after he missed the entire 2011 season, the biggest thing on Manning's mind was working with his new snapper.
So, he and Walton spent endless hours practicing on local high school football fields before they could work out at the Broncos' headquarters.
''That's probably the first thing I did when I got here, was getting snaps with J.D. The quarterback-center exchange is vital, and so I'm sick about his injury,'' Manning said Wednesday. ''When you lose a starting center who has started every game for the past three years, it's very rare that you can replace him with a veteran like Dan who has played in many huge games and is experienced. So we feel fortunate to have him and it's always nice having a veteran player who's been around winning for his entire career on your team.''
Indeed, the Broncos didn't miss a beat Sunday when Koppen came in just before halftime and played the rest of the way as Denver outscored Oakland 27-0 in the second half of its 37-6 rout of the Raiders. He helped Manning record his first sackless day as a Bronco and his second straight 300-yard passing game.
Walton, who had missed only one offensive snap in his career, out of 2,269 possible plays, got hurt when defensive end Jack Crawford inadvertently crashed into his legs as he was making the tackle on running back Lance Ball.
Walton didn't speak with reporters Wednesday when he walked through the locker room on crutches with his left leg in a protective boot.
Koppen signed with the Broncos three weeks ago after spending his entire career in New England, where he'll make his first start Sunday in a pivotal matchup of 2-2 teams with high hopes that can ill afford another stumble.
Patriots quarterback Tom Brady said it'll be weird seeing Koppen snapping the ball to Manning.
''Being one of my best friends over the years, to see him go was a very hard thing,'' Brady said. ''But I was happy he really got the opportunity to be with a great organization and to play with a quarterback like Peyton and certainly with an offense like that, I'm sure Dan's a great fit.''
Koppen started 134 games for the Patriots, including the playoffs, before breaking a bone in his lower left leg in the opener last season. He spent the rest of the year on injured reserve and then lost a competition to Ryan Wendell in training camp.
The Broncos signed him three weeks ago.
''It's been great. We haven't been together too long yet, but I'm sure glad we brought him in,'' coach John Fox said. ''At no point were we thinking he'd be lining up as the starting center as we head into Foxborough this weekend.''
The Broncos are set to get right guard Chris Kuper back from a broken left forearm that sidelined him most of the preseason and the first month of the regular season.
With Kuper and Koppen, the experience quotient in Manning's pocket of protection rises exponentially.
''He won a lot of games and has some great experience,'' wide receiver Eric Decker said of Koppen. ''So, to have him around is just going to make us better.''
Koppen said that while he's got a long way to go, he's already comfortable in Denver's offense.
''I'm pretty familiar with it. I think it's along the same lines of what we ran in New England, which helped. Just a little bit different verbiage and all that stuff,'' Koppen said.
He's taking his homecoming in stride, too.
''I'm sure it's going to be fun. A little bit different, a little bit of a different view, but it's still just football,'' Koppen said.
Notes: The Broncos had their first perfect attendance at practice this season on Wednesday although Kuper and LB Nate Irving (concussion) were limited. ... Broncos FB Chris Gronkowski on facing his brother, Patriots TE Rob Gronkowski, and who his parents will be rooting for: ''I keep asking them who they're cheering for and they won't tell me, so we're going to have to see on game day what jersey they're wearing.'' ... K Matt Prater won his fourth career AFC Player of the Week award after kicking three FGs against Oakland and putting all 8 kickoffs out of the end zone for touchbacks.
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