ENGLEWOOD, Colo. (AP) Shortly after the Denver Broncos received new orange T-shirts reading ''Keep Your Feet,'' the most expensive ones on the field got tangled.
When Peyton Manning took the snap and turned to hand off, the quarterback and the football both hit the turf.
Manning is getting used to being under center again as he adapts to coach Gary Kubiak's run-oriented, play-action offense with all its rollouts, handoffs and mobile pockets.
As for the fall, ''I don't remember that happening,'' Manning feigned through a mischievous grin Wednesday, saying video director Steve Boxer had already erased the evidence.
''That's the advantage of being tight with your video guys,'' Manning said.
Kubiak had a hard time getting the image out of his mind.
''The one thing the league always wants you to do is keep players off the ground. So, we preach it, we preach it, we give out T-shirts today saying `Keep Your Feet' - he's the first one to hit the ground,'' Kubiak said. ''So, yeah, we're giving him a hard time.''
Manning, who has been much more comfortable operating from the shotgun late in his career, is coming up to the line of scrimmage on almost all of his snaps right now.
''We know the other end of the stick is fine. It's something he's been doing forever,'' Kubiak said. ''So, we're going to spend a lot of time under center initially. ... He's been very responsive and he's working extremely hard.''
After what he called the Broncos' ''first real day of practice in shoulder pads,'' Manning said he's eager to smooth out the roughness in this new hybrid offense, saying, ''I feel I can do whatever they ask me to do.''
Manning ended 2014 on a down note, affected by both a thigh injury and the old coaching staff's wholesale shift at midseason in both his pocket of protection and run/pass ratio.
As he contemplated his future over the winter, pundits said Manning's arm strength wasn't what it used to be.
He looked strong and sharp Wednesday, whistling throws whether short, medium or long. He looked quick on his feet, too - save for the one tumble - and also appears to be in top condition, especially at 39.
Strength and conditioning coach Luke Richesson recently mentioned at a clinic that Manning was hitting personal bests in all his weightlifting numbers, high praise that quickly found its way through Twitter.
Conventional wisdom suggests that quarterbacks are more cozy in the shotgun because they don't have to take their eyes off the pass rush, have more time to react and can more easily decipher defenses.
Not necessarily, Manning said.
''Under center you can keep your eyes on the defense a little longer, to tell you the truth,'' he said. ''Whereas in the shotgun, you've got to put your eyes on the ball at some point'' as it's snapped.
Manning is also getting accustomed to a new offensive line.
On Wednesday, the first unit included three veterans who weren't starting in Denver last year: Ben Garland, Gino Gradkowski and Chris Clark. Also, blindside protector Ryan Clady sat out the last portion of drills after a trainer tended to his left leg. He was replaced by second-year player Michael Schofield.
Manning said he's been in regular contact with wide receiver Demaryius Thomas, who is boycotting the Broncos' offseason program after the team placed its $12.8 million franchise tag on him.
The friend in him wants Thomas to get as big a long-term contract as he can. The football player in him wishes Thomas were here running routes opposite Emmanuel Sanders.
''I want what's best for him, I really do,'' Manning said. ''And I hope there's that happy medium for both sides and we can get him in here soon and put that all behind everybody.''
Manning was still smiling over his appearance on David Letterman's final show last week. He was part of the Top Ten, a constellation of comedic stars who told the late-night icon what they'd always wanted to say to him.
''You are to comedy what I am ...'' Manning told Letterman, ''to comedy.''
Standing between Steve Martin and Bill Murray, Manning said he knew ''I'm out of my league.''
''All I know is that Seinfeld told me I had a good line. So, if Jerry Seinfeld tells you you've got a good line, that means you've got a great line. That's the ultimate compliment there.''
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