Peyton Manning is leaving some big cleats to fill as the premier NFL pitchman, but experts are eyeing brother Eli to take over the signal calling.

It’s not a given — even though third-ranked Eli trailed Peyton’s league-leading $12 million in off-field income last year by just $4 million.

Drew Brees of the New Orleans Saints came in second with $11 million, while Aaron Rodgers of the Green Bay Packers was fourth with $7.5 million.

Sports marketers recognize both quarterbacks as worthy advertising adversaries to the Giants’ Eli but give Peyton’s little brother the edge for playing in a media capital.

“You’re going to have to see the others in more Super Bowls,” said Ben Sturner of sports-marketer Leverage Agency.

By comparison, the Giants’ fan base, coupled with Eli leading the Giants to two Super Bowl victories, guarantees a degree of visibility marketers love.

“They both excel at that,” said Brandon Steiner of Steiner Sports Marketing. “That’s why you have to start with Eli [as lead NFL endorser] now that Peyton’s gone.”

Eli’s reign as the supreme endorser may not last long, however.

“The next iteration of brand marketing will embrace deeper, more explosive personalities that appeal to a younger audience,” David Schwab of Octagon First Call told The Post.

Schwab then predicted the Carolina Panthers’ quarterback — the brash but charismatic Cam Newton — will attract enough brands envious of his personality to ascend to the advertising throne.