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Peyton Manning's arm strength looks just fine. It's his timing with his new targets that's the biggest question mark facing the four-time MVP as he embarks on his comeback with the Denver Broncos.

Manning doesn't appear bothered by the nerve injury in his neck that led to a series of operations, sapped his power and sidelined the league's most durable active quarterback all of last season.

Ever since he signed with the Broncos on March 20, two weeks after his tearful release from the Indianapolis Colts, Manning has been working hard to refine his rapport and rhythm with his new corps of pass catchers.

He has two old pals from his days in Indianapolis to help him adjust in wide receiver Brandon Stokley and tight end Jacob Tamme.

And he has two of the most promising young receivers in the NFL in third-year pros Eric Decker and Demaryius Thomas, the biggest downfield threat he's ever had.

They lead a deep group of players vying to become the next Reggie Wayne or Marvin Harrison in Manning's aerial show.

"We always talk the opportunities are the greatest right now," Decker said. "We have a future Hall of Famer, a guy who's been to the Super Bowl, an All-Pro, someone who wants to win, too. I think as young receivers, we're hungry, we want to make the most of this opportunity and play our best football this year."

Catching Manning's passes is a thrill for a group of guys who loved Tim Tebow's passion but weren't exactly fans of his erratic passing.

Manning is a perfectionist whom running back Lance Ball called a "player-coach," a description Decker finds appropriate because Manning is that rare breed of superstar who makes everyone around him better.

"It's been great. He's definitely a leader," Decker said. "This guy's going to demand the best out of himself and the best out of his teammates. I think a lot of guys respond to that."

Although he put in hours on local high school football fields playing catch with Stokley and Decker, among others, Manning laments that he only had 17 organized offseason practices to adjust to his new team.

So, he was among the most enthusiastic when training camp got here.

"Now, it's fulltime football," Manning said, the relief evident in his voice.

The Broncos, whose workout Friday was interrupted by a nearby lightning strike, will have 17 practices before they open the preseason at Chicago on Aug. 9.

Manning will be padded up Saturday morning for the first time since playing in his 11th Pro Bowl following the 2010 season.

Before last season, the 36-year-old quarterback started all 277 of the Colts games, including playoffs, during his first 13 years in the league.

He's never faced this much doubt about his durability, or, for that matter, his ability.

Coach John Fox swears he's not among those questioning whether Manning will hold up.

"I worry about all of them but not because of any past injury," Fox said.

Manning said his rehab is a work in progress, and he declines to discuss specifics for competitive reasons, but he said his focus right now really is on developing a rhythm with his receivers.

Decker is the one who's spent the most time on the other end of Manning's passes in Denver, and he said he already sees that work paying off.

"I think every chance you get" to catch Manning's throws "it just makes you better down the road," Decker said.

Manning said it's the Broncos' collection of experienced cover cornerbacks — Champ Bailey and newcomers Drayton Florence and Tracy Porter — who will really help Denver's young receiving corps blossom.

Although Andre "Bubba" Caldwell has the speed and shifty moves to push for prime playing time, the Broncos are eager to see what kind of years Decker and Thomas can put together with Manning under center.

Neither has been able to put together a complete season in the NFL. Decker shined for two months last season but faded after Tebow took over at quarterback for Kyle Orton. Thomas missed the first half of the season with a torn Achilles tendon and a shattered thumb but was unstoppable down the stretch.

Decker went down with a knee injury early in the Broncos' wild-card playoff game against Pittsburgh, and Thomas stepped up with four catches for 204 yards, including an 80-yard TD catch from Tebow on the first play of overtime.

Thomas had to undergo another operation to remove pins from his left thumb this offseason. So, he was sidelined once again when Manning signed with Denver and immediately began throwing passes to Decker, his new workout buddy.

Thomas insists he wasn't jealous that Decker formed a rapport with Manning sooner than he had the chance to do.

"I basically just wanted to come in healthy and whenever I started, I started," said Thomas, who returned to the field in May and has been doing yoga in hopes it will help him stay healthy for a change.

Thomas has some catching up to do.

"I'm getting to know Demaryius," Manning said. "I think you see that just like me, there's different phases. There's a minicamp/OTA sort of tempo and then there's training camp, preseason, regular season and you hope playoffs. So, I'm looking forward to getting to know all these guys throughout the different phases of a season, and obviously trying to do my part throughout the different phases. But Demaryius is going to play a key role for us this year. I thought he came back in great shape."

Manning may be new to Denver, but he's already a sage in the locker room, fielding a steady stream of queries from cornerbacks curious about how he deciphered a particular defense to receivers pursuing pointers.

"I like being around young players," Manning said. "I mean, they're all young compared to me. Stokley and I were talking, and it's fun being around these guys who are 22, 23. It keeps you kind of feeling young and feeling into it.

"It's humbling at times when they say they enjoy seeing you play on ESPN Classic. That's not exactly what you want to hear. But I do enjoy getting to know these guys, and that part has been fun for me."

Notes: The Broncos were forced to move practice indoors after lightning struck near their Dove Valley complex just minutes into Friday's workout, much to the disappointment of the nearly 3,000 fans on hand. "We were a little disappointed that we weren't able to come back and practice in front of them, but we still had a productive day," LB Joe Mays said. ... Starting S Quinton Carter injured his right hamstring trying to break up a pass from Manning to TE Joel Dreessen and limped off the field at the South Suburban Sports Dome.

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Follow AP Pro Football Writer Arnie Stapleton on Twitter: http://twitter.com/arniestapleton