Sources: Peyton Manning making encouraging progress with his arm strength

Three NFL sources that have seen medical reports on quarterback Peyton Manning say the improvement of his arm strength appears to be going at a promising pace, although a full recovery is still far off.

"So far, so good," said a source with one of the many teams that is interested in signing Manning. "The question is still where is it going to stop, but the progress over the past month has been steady and that's what you're looking for."

[ Report: Chiefs have made contract offer to Peyton Manning ]

There had been some fear in late January that Manning's recovery had stalled. While that appears to be a subject of interpretation at this point, the progress over the past month has been sufficient enough that any team seeing the information would likely be willing to continue its pursuit of Manning, who was released Wednesday by the Indianapolis Colts.

"This is not a physical and he hasn't taken one with us yet," the source said. "There are still a lot of questions to answer before you continue on, but this information is promising."

Information was gathered from both Manning's personal physicians and the Colts, who have sent all relevant information to teams that are interested in Manning.

"Some of this stuff is in the eye of the beholder," another source said. "I don't think there's anything there that would discourage you from going forward, but you'd have to consider the risk.

"Is this a situation where I would hand the guy [a lot of guaranteed money]? No, I would be hesitant because there's still a ways to go … really, that stuff is outside my expertise, but it's hard to know for sure that he's absolutely going to be ready at a certain time. I think he'll be OK, but I don't know exactly when."

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Yahoo! Sports Radio: Jason Cole on downside to signing Peyton Manning]

All three sources said the concern at this point is all about the nerve and strength regeneration in Manning's right throwing arm. The cervical fusion in his neck is solid enough to continue playing football.

"The neck is as good as you would expect for anyone who has played that long," the second source said. "It really comes down to the arm."

The question for all teams will be whether Manning throws for them (at least one team appears ready to sign him without having him throw) and how effectively he throws. The video clip of Manning throwing at Duke University last week is hardly considered adequate evidence.

[ Jason Cole: Peyton Manning's presence stealing Matt Flynn's thunder ]

"He threw one 40-yard pass," the first source said. "How would he do if he threw two more? How does he throw if he doesn't get to plant his feet and get his weight into it? How does he throw when he's backpedaling and it's all arm strength? There are a lot of questions left to be answered."

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