Aaron Rodgers and Peyton Manning have crafted careers wholly apart, empires rising across a vast sea. They shared an era without overlap and coexisted in separate spheres. Rodgers and Manning, two of the greatest to play the most glamorous position in American sports, squared off on Oct. 19, 2008, in Rodgers’s first year as the Green Bay Packers’ starting quarterback. He trounced Manning’s Indianapolis Colts, 34-14. They have not shared a field since.

Rodgers provides a measuring stick for current quarterbacks, but Manning has receded, diminished by injury and age, to the point that he cannot compare his present ability to Rodgers’. Manning provided an idol for a generation of quarterbacks, but somehow Rodgers slipped through that crack. “No disrespect,” Rodgers said this week. “I haven’t seen a ton of film on him over the years.”

Sunday night, then, will provide an encounter for football historians to savor. Manning and Rodgers will meet at Denver’s Invesco Field. Both will lead 6-0 teams with a chance to represent their conference in the Super Bowl. After more than a decade of carrying teams, Manning, 39, has been carried by his defense. In his eighth season as a starter, Rodgers, 31, is operating at a level rarely witnessed.

Like they enter Sunday night at different stages of their careers, Manning and Rodgers occupy different places in the position’s history. Nearing the end, Manning stands as a revolution. Reaching the apex, Rodgers represents an evolution.

Manning changed how quarterbacks play. In a response to football’s rising complexity, Manning made the position as much about thinking as action. He distilled endless preparation into a flawless dissection of an opposing defense. Manning’s skills and habits made playing quarterback as much about what the quarterback can see before the play as what he can do during.

In “The QB,” his book on modern quarterbacks, author Bruce Feldman recounted a story from Manning’s college days. His Oldsmobile Bravada had become so packed with game tapes that he needed to unload some at Tennessee’s football office. There was enough to fill a shopping cart.

“We saw the position become a lot more cerebral,” Feldman said. “It’s not that Joe Montana wasn’t cerebral. But I think things became a lot more complicated with defenses. They put a lot more on the QBs to have answers to different things.”

Rodgers has not fundamentally changed the position. He just does everything required of an NFL quarterback better than almost everyone else. He studied Brett Favre’s boldness and creativity up close and tucked it all in a rare physical package. Rodgers is a collection of the best traits of a quarterback, amplified.

Upon entering the NFL, Rodgers served as Favre’s understudy for three seasons. This week, he said he studied far more than Manning, the standard beacon for his peers. Favre was “unconventionally talented,” Feldman said. He freewheeled and improvised and used his rocket of an arm to get away with decisions and throws other quarterbacks couldn’t dream of. He was the anti-Manning – he didn’t have to think much because his arm would bail him out of trouble.

From Favre, Rodgers learned he could frustrate a defense by going off script. When Rodgers ran the scout team, he told Feldman in an interview for “The QB,” he would annoy defensive coaches by improvising plays, experimenting with new ways to confuse the defense.

Rodgers also developed unconventional talent of his own. His quick release is legend. He pairs it with uncanny body control and wicked arm strength. He has the quickness to find room within the pocket and enough speed to punish a defense if it leaves the middle of the field available. If you paused film of Rodgers scrambling and tried to guess where he might throw, even a second before his release, it would be a fool’s errand. His athleticism allows him to make whatever throw is required, from any position.

It is the quality that differentiates Rodgers from Manning. Manning can solve a defense and beat it at its own game, figuring out what it wants to do and then exploiting a weakness. Rodgers can do that, too, but he can also invent.

“Rodgers takes of advantages of defenses because he’s doing things they don’t think he should be able to do,” Feldman said. “That’s the part that separates him.”

Even if Rodgers does not pattern himself after Manning, he recognizes the grandness of his career. He revamped so much, from how a quarterback stands at the line of scrimmage to how he becomes a pitchman. (“I think Aaron has some nice spots,” Manning said this week.) If the Broncos upset Green Bay on Sunday night, Manning will tie the all-time record for wins by a quarterback – a mark held, coincidentally, by Favre.

“Longevity is usually only achieved through consistency,” Rodgers said. “Manning has done it for such a long time at a high level. He’s been the standard for quarterbacks.”

The old standard is fading, and even he seems to understand that, if not confront it head on. Through six games, Manning has thrown 10 interceptions and seven touchdown passes. The formula used by Pro Football Focus, a leading analytical web site, rates Manning the NFL’s 24th-best quarterback this season, between rookie Marcus Mariota and Washington’s Kirk Cousins.

During a media teleconference this week, a Green Bay reported asked Manning to evaluate himself. Manning replied that he had been reading a devotional about talking about others and not yourself. “I’m abiding by that devotional today,” Manning said. “For me to talk about myself, it just puts me in an uncomfortable position.”

Manning’s tenure as the standard may have already elapsed. In researching his book, Feldman traveled to quarterback camps and observed elite prospects, the next wave to follow. “To see some of the stuff they do,” he said, “I think a big idol for a lot of these guys is Aaron Rodgers.”