By Jason Keidel

If NFL history has taught us anything, it’s that when you have more than one starting quarterback, you have none at all.

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Recall any of the great teams in the Super Bowl era. Almost all of them were set in the single most important position. There is no Steel Curtain Steelers without Terry Bradshaw. No Walsh Niners without Montana. No 1990s Cowboys sans Troy Aikman. And no one doubts the eminence or importance of Tom Brady during New England’s 15-year run among the top rungs of the sport.

Denver is challenging that coda. After losing Peyton Manning to retirement and then Brock Osweiler to a swollen offer from the Houston Texans, they’ve embarked on a shopping spree for high-end QB talent.

To this point, that has led them to Mark Sanchez, he of Butt Fumble fame. For the world west of the Hudson River, Sanchez had a sublime start to his career in the Big Apple, reaching the AFC title game in his first two seasons. Then he, like the Jets and Rex Ryan, crumbled under the weight of hubris, high expectations and the blinding lights of America’s media vortex.

Sanchez gave the Eagles a shot, and that failed. So Denver’s banking on some kind of revival in the high, thin air of the Rockies.

But knowing Sanchez’s dubious history, John Elway won’t stop there. The Hall of Fame QB and similarly gifted GM is now in talks with another forgotten quarterback whose descent was as meteoric as his ascent.

Colin Kaepernick, who, like Sanchez, charmed a major American city, is on the chopping block. He’s being shopped by the team that made him a star. Not that long ago, Kaepernick was the very model of the new-world QB that seemed close to forever changing the sport.

Then John Harbaugh was jettisoned, and, with the ornery coach, followed much of Kaepernick’s name, game and mojo.

It wasn’t just Harbaugh, of course. Like all teams that make a hard run and hover around the Super Bowl for a few years, the 49ers were poached by the competition. And, between age, wage and injuries, the studs started leaving the roster. Gone were stalwarts Frank Gore, Patrick Willis, Donte Whitner and Michael Crabtree, among others. Even Willis’s replacement as top dog of defense, NaVorro Bowman, suffered a grotesque injury that shelved him for a year.

So, fair or not, Kaepernick is now seen as little more than a Harbaugh contrivance, the main act in a circus that left town two years ago.

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No matter the reason for his fall, Kaepernick’s game has clearly decayed. All those 40-yard romps toward the end zone have been snuffed out. His howitzer for a throwing arm, which he so often kissed after a touchdown, has been muffled.

You’d think someone with his resume would enjoy a fresh start with a QB guru like Chip Kelly, who bounced westward after an inelegant divorce from the Philadelphia Eagles. With the dearth of decent QB talent around the league, Kelly should be frothing over a chance to retool someone with Kaepernick’s skill set.

Yet here we are, under a shower of online reports that the only thing keeping Kaepernick from Denver is a few million bucks.

Everyone who has reached a high level of success thinks they have the secret sauce. And when you consider the crossover success Elway has enjoyed, from the gridiron to the executive suite, he may think that he and his hand-picked QB whisperer, Gary Kubiak, can fix a fellow No. 7.

Denver also just won a Super Bowl with a rather diminished Peyton Manning, who was reinserted into the lineup two months after a disastrous game against the Kansas City Chiefs. He was benched under the guise of a foot injury. But it may have been a binary problem, equal parts limb and mind.

What the Sheriff’s return brought to the Broncos was a sense of stability and unity at the top. While Brock Osweiler did fine as Peyton’s replacement, there was little sense that he could lead them to a Super Bowl title. And even if Manning was a fraction of his former brilliance, there was comfort in seeing a five-time NFL MVP under center.

The residual damage, of course, was a jilted Osweiler, who shocked the Broncos by fleeing to Texas. We’ll never know if he would have slid seamlessly into Peyton’s place. But we do know that recruiting retreads like Sanchez and Kaepernick is a perilous approach.

Denver is experiencing the very attrition that all Super Bowl winners suffer. They’ve lost several key defensive players, which is to be expected. But they also have an epic void at quarterback. Something no one expected two months ago. Seattle won a Super Bowl but still had Russell Wilson. The Ravens retained Joe Flacco. And the Patriots still have the ageless Brady.

So Denver faces more hurdles than most Super Bowl winners. And if it all hinges on the rise of the Sanchise or the inked-up, bulging biceps of Colin Kaepernick, they could be in for a long, lean year. Unless Elway has a few bombs left in his blessed right arm.

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Jason writes a weekly column for CBS Local Sports. He is a native New Yorker, sans the elitist sensibilities, and believes there’s a world west of the Hudson River. A Yankees devotee and Steelers groupie, he has been scouring the forest of fertile NYC sports sections since the 1970s. He has written over 500 columns for WFAN/CBS NY, and also worked as a freelance writer for Sports Illustrated and Newsday subsidiary amNew York. He made his bones as a boxing writer, occasionally covering fights in Las Vegas, Atlantic City, but mostly inside Madison Square Garden. Follow him on Twitter @JasonKeidel.