This is not a column about Tim Tebow and the Eagles, really. This is not about whether he'll beat out Matt Barkley for the No. 3 quarterback spot or whether Chip Kelly will use him in short-yardage or special-teams situations or whether his throwing motion is quicker and tighter and no longer resembles Sandy Koufax working out of the stretch. This is not a column about the minutia of football we tend to focus on when we focus on the Eagles. Feel free to stop reading. No one will be offended.

This is a column about business and the power and mystery and marketability of an athlete's image, because while no one knows for certain if Tebow will have a role with the Eagles this season or, if he does, what that role will be, we do know this: He had that power, and over the last 21/2 years, he has lost a lot of it. It has been a remarkable and precipitous fall, given where he stood on March 26, 2012, the day that he and America may have achieved Peak Tebow.

That afternoon, after having acquired Tebow in a trade with the Denver Broncos five days earlier, the New York Jets introduced him with a press conference inside their Florham Park, N.J., training facility - more than 200 white folding chairs arranged in perfect rows to accommodate all the media who attended. As Tebow answered questions, two executives with TiVo Inc. traveled from the company's San Jose headquarters to Beverly Hills to meet with representatives from William Morris Endeavor Entertainment, the talent agency that represented Tebow at the time, to explore an endorsement agreement - one that Tebow and TiVo later consummated and have maintained since.

The juxtaposition of those two events, happening simultaneously, illustrated the unique brand of stardom that Tebow had achieved - through his accomplishments at the University of Florida, through the prosthelytizing nature of his Christianity, without even demonstrating that he could be a competent NFL starting quarterback over time. More, it showed the potential he had to leverage that stardom within the nation's biggest media and financial market.

The potential went unfulfilled. Tebow saw the field for just 77 offensive snaps with the Jets, and he hasn't appeared in an NFL game since they released him in April 2013. He had endorsement/sponsorship deals with five companies then. At least three of those deals--with Jockey, SOUL Electronics, and The FRS Company, which sells energy drinks--have expired. ("The agreement between Tim and Jockey ran its course," a company spokesman said, which makes you wonder: What good did Tebow's infamous shirtless run in the rain at Jets training camp do him?) Nike did not respond to several requests for comment. William Morris doesn't represent Tebow anymore.

Tebow did appear in a T-Mobile television ad during Super Bowl XLVIII in February 2014. But the ad's title, "No Contract," and premise (showing Tebow in various professions other than football player) were based entirely on his absence from the NFL.

"It was fun," he said, "because I got to let a little of my personality come out."

Now that he's back (at least for a while) in what is likely to be a limited role with the Eagles, the true force of his celebrity promises to be put to the test.

"He's a very interesting case study for this kind of thing," said Jim Andrews, senior vice president of IEG, an advertisement and sponsorship consulting firm. "With him, it's not just about the athletic abilities. Is there the potential for him to be back in that spotlight as a starting quarterback in the NFL for a winning team? That's one way to look at it. Do we think that's going to happen, or is he going to be a guy on the sidelines with a baseball cap and clipboard? In that case, we're not as interested."

After Tebow's failed 2013 tryout with the New England Patriots, it became difficult for anyone, let alone a business looking for an endorser who could draw in customers, to see Tebow without the cap and clipboard. Backup quarterbacks generally don't make particularly attractive pitchmen. Third-stringers are even less useful. A guy who can't earn a roster spot . . . forget it, even if a sizable portion of the population views him as the walking, talking, Tebowing embodiment of all that is good and righteous and pure in life and sports.

Still, Tebow said the dissolution of some of those partnerships did not bother him: "I had really good relationships with a lot of those people. For me, it's deeper than just an endorsement, deeper than just being a spokesperson for a brand. It's the people behind it, too."

There is one company that has remained unflagging in its belief in the appeal of Tebow's persona. On its Facebook page, TiVo has released a series of 15- and 30-second ads as part of a new campaign. Each ad is set in a doctor's office, and on a table in the office is a framed photograph that is visible for no more than a heartbeat before the camera cuts to another shot. You have to look hard, but it's there.

The photo is of Tim Tebow's face.

msielski@phillynews.com

@MikeSielski