Peyton Manning has been medically cleared by two doctors -- one of whom performed the most recent surgery on the Colts quarterback's neck -- to resume his NFL career, sources told ESPN's Chris Mortensen and Adam Schefter.

On Indianapolis' front, the good news was tempered by Colts owner Jim Irsay, who tweeted that "Peyton has not passed our physical nor has he been cleared to play for The Indianapolis Colts."

The sources said Dr. Robert Watkins, who performed the procedure on Manning, examined the player recently in Los Angeles and concluded the stability in his neck would have allowed Manning to play this Sunday as long as the nerves in his arm had regenerated to a satisfactory performance level.

Watkins also instructed the quarterback to continue an aggressive rehabilitation path that provides an optimistic outlook for Manning to play in 2012. Watkins performed Manning's spinal fusion Sept. 8, and on Dec. 1 declared that the fusion had achieved "firm fixation."

Watkins, according to the sources, joined Colts neurosurgeon Dr. Hank Feuer in clearing Manning to play. One source said that Feuer recently told Manning, "If you were my own son, I'd tell [you] to go play."

A spokesman for Watkins said in a one-paragraph email sent later Thursday night that the Colts' star was cleared to play.

"Peyton Manning underwent a thorough medical re-evaluation as part of a postoperative visit with his surgeon," Watkins' statement read. "As a result of this examination, Manning is medically cleared to play professional football."

Irsay said a team statement would be forthcoming later Friday.

Commissioner Roger Goodell, speaking Friday during his annual pre-Super Bowl news conference, said he's "not troubled at all" by all of the Manning talk during Super Bowl week, and doesn't believe it has been a distraction.

Goodell said he understands why there's so much interest in Manning, given that he's such an important player to the league and the community.

In addition to Manning's optimistic words expressed in an interview Tuesday with ESPN -- in which he indicated he plans to resume his playing career -- the medical clearance by his two doctors, the sources said, will bolster his determination to play in 2012.

What remains in question is the timeline in which Manning's nerve regeneration to his triceps will improve to the point where he is throwing passes in the manner that helped him win four MVP awards during his 13-year career.

According to one source familiar with Manning's medical review, "It's not a safety issue; it's a performance issue." This source added that Manning is "making progress."

The source said Manning had a throwing session Tuesday with two of his Colts receivers -- Anthony Gonzalez and Blair White -- at an undisclosed location and that Manning has spent numerous recent days throwing to at least one wide receiver, aiming to regain as much strength as possible in his arm.

Peyton Manning was cleared to resume his career Thursday, according to sources. Joe Robbins/Getty Images

However, the source said Manning still cannot pinpoint a date when his performance will reach an acceptable level to him. The source alluded that it might take to the one-year anniversary of Manning's May 23, 2011, surgery on a bulging disk in his neck.

Manning and Colts owner Jim Irsay have both said they expect to sit down after the Super Bowl to discuss his future with the team as a March 8 deadline nears in which Manning is due a $28 million option bonus that will trigger the final four years of a five-year, $90 million contract he signed before the 2011 season. The quarterback already received $26 million as part of that deal.

Manning has expressed a desire to settle his future with the Colts "sooner than later." There is widespread belief around the league that Irsay will not exercise the $28 million bonus. Irsay was not available for comment.

Yet should the Colts opt not to exercise the option, they would be forced to release Manning, who would immediately become a free agent. And so, while the NFL's free-agent signing period is set to begin with the commencement of a new league year March 13, Manning could be a free agent as early as next week.

If Manning becomes an unrestricted free agent, several teams are expected to bid for him, including the Washington Redskins, Miami Dolphins, Arizona Cardinals and possibly the New York Jets, among others.

Teams such as Arizona already have debated the merits of pursuing Manning behind closed doors. Some people within the Cardinals organization believe Manning could do for Arizona what Kurt Warner once did, propelling the team into an instant playoff contender.

Manning likely would be willing to sign a contract that would tie bonuses and salary to his roster status for 2012, and sources say that he will heavily factor in a team's ability to have a roster capable of competing for a playoff spot and, consequently, a Super Bowl title.

Trading Manning no longer is an option. Irsay has said he will not trade Manning -- which means he would have to pick up the $28 million bonus to retain the quarterback's rights -- and he also will not trade the No. 1 pick in the April draft, when the Colts are expected to select Stanford quarterback Andrew Luck or possibly Baylor quarterback Robert Griffin III. Many NFL executives expect Luck to be the pick.