It has been widely assumed by those in and around the NFL that the Denver Broncos and executive vice president and general manager John Elway desperately desire the return of quarterback Peyton Manning.

It was reported early Tuesday that the soon to be 39-year-old Manning had begun training with noted fitness guru, Mackie Shilstone, in a preliminary effort to return to the NFL and the Broncos next year.

Only Manning may be making an effort not entirely appreciated by Elway and the rest of the Denver brass.

"In talking to sources close to the team and around the team, there is a big question here about whether the Broncos want to bring him back for one more year and they're going to have to feel very comfortable about this," said Bleacher Report's Jason Cole.

Manning, despite his advanced age and growing injury history, was still one of the most effective quarterback's in the league last year, finishing the regular season with 4,727 yards, 39 touchdowns and 15 interceptions.

He led the Broncos to an AFC West crown and playoff berth before proving surprisingly ineffective in the team's second-round, postseason loss against his former squad, the Indianapolis Colts.

While it's promising and admirable that Manning is attempting one more go-round with his increasingly fragile body, Elway and the Broncos are no doubt concerned with the drop off in his player later in the season.

"It's fantastic that Peyton Manning is doing all these things intending to play but ultimately the final decision about whether he plays in Denver next season is up to the Broncos and up to John Elway because Peyton is going to have to take a physical before the end of this year in order for his salary in 2015 to guarantee," said Cole, who notes that the team could very well fail Manning during that pre-season physical.

With the unproven Brock Osweiler the only other option currently on the Broncos roster, it's hard to envision Elway turning down an offer from Manning to play one more season, but should another avenue for quarterback improvement present itself, perhaps the unthinkable becomes reality.