ENGLEWOOD, Colo. — As the Denver Broncos ran out the clock in their win over the San Diego Chargers last weekend, football fans gasped as Peyton Manning, the undisputed face of the N.F.L., got up limping after being tackled around his legs.

The injury turned out to be only an aggravation of an earlier ankle sprain, and Manning said he would play Sunday in a prime-time showdown with the undefeated Kansas City Chiefs, who are atop the A.F.C. West, one game ahead of the Broncos.

Yet the concern over Manning’s health was a reminder of how valuable he is — not just to the Broncos, but the entire league. On pace to win a record fifth Most Valuable Player award and perhaps lead the Broncos to the Super Bowl for the first time in 15 years, Manning is a proven leader on the field, and a winner off the field, too.

He is the country’s best-known football player, the successor to Dan Marino, John Elway and Brett Favre, who all held center stage during their prime. Sponsors crave his aw-shucks grin and seemingly spotless personal life, and a raft of endorsement deals, including for Buick, DirecTV and Papa John’s, keeps him in the spotlight on nongame days.