There's a reason Peyton Manning is working with a specialized trainer.

The New Orleans Times-Picayune quoted an anonymous source as saying that the Denver Broncos quarterback has been training in preparation for his 18th NFL season.

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Fitness trainer Mackie Shilstone, who specializes in working with older athletes to develop a regimen geared toward career extension, has evaluated Manning and is working with the quarterback who will turn 39 next month.

Manning has spent his offseason so far seeking medical evaluations on his surgically repaired neck, as well as a thigh injury that hampered him during the second half of the 2014 season. According to the report, he has been trying to determine whether he would be able to withstand the physical toll of another NFL season.

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The Times-Picayune added that Manning has his neck checked each season since he had surgery on it in 2011 and missed the entire season with the Indianapolis Colts. He left for the Denver Broncos in 2012.

The Broncos requested that Manning let them know of his 2015 plans by March 9. That's when he would be due $19 million for next season. The Times-Picayune reported that Manning wants to talk to general manager John Elway before announcing his intentions for next season. Manning hoped to talk to Elway in the next "couple of days," according to the newspaper.

New Broncos offensive coordinator Rick Dennison said the team isn't in a rush before March 9 to have Manning decide whether he wants to return. Speculation arose that the Broncos would not be able to build a playbook without knowing who the quarterback will - or won't - be.

"I don't think so, we're going to go see what we do best, see what our team ends up with, there's certainly no rush," Dennison told reporters, according to NFL.com. "He deserves to take his time and figure out what he wants to do because he's a phenomenal player.

Shilstone has trained hundreds of professional athletes over the years, including boxers Roy Jones Jr. and Bernard Hopkins and most notably tennis superstar Serena Williams, the Times-Picayune added. Baseball Hall-of-Famer Ozzie Smith acknowledged Shilstone in his induction speech and credited the trainer with adding 11 years to his career.

Manning is 2,148 yards away from breaking Brett Favre's NFL career passing-yards. Manning surpassed Favre in career touchdown passes during the seventh week of the 2014 season.