But one thing is certain: It won't fail because of lack of effort.
The quarterback has been throwing at an up-tempo pace since mid-December, just before his attempt to return for the Indianapolis Colts' final two games finally ended, as SI.com reported Wednesday. Manning threw in a post-practice setting with a group of receivers and running backs Dec. 14 as part of the rehabilitation process.
One league source said that to "describe it as a practice is incorrect." The session was scripted by the Colts' strength and conditioning coaches and Manning's rehabilitation coordinator, with then-vice chairman Bill Polian, coach Jim Caldwell and offensive coordinator Clyde Christensen monitoring from the sideline.
According to the source, Manning was throwing at about "85 percent" and didn't seem impaired, though the players were constrained to an area inside the 25-yard line so the quarterback wouldn't have to (or be tempted to) make more taxing throws.
Four days after the session, Polian announced that Manning wouldn't play at all in the 2011 season. At the time, Polian said Manning hadn't "come far enough to make it prudent for him to step on the field in game action."
Doctors consistently told Colts officials to be careful in charting Manning's progress throwing the ball, especially after that work in December. The doctors maintained that while Manning's neck issue had cleared up, the problem with nerve regeneration remained, and there wasn't a timetable for recovery in that area.