Jeremy Piven -- Peyton Manning's Crappy Game ... Won't Kill Pitchman Career

Before the Super Bowl, Jeremy Piven said Peyton Manning was the GOLD STANDARD for a celebrity pitchman -- but after his pathetic performance, is Peyton's star falling in Hollywood?

Piven was leaving Freewheel Sports in Larchmont today and made a strong case for why Peyton's still the man ... but not everyone's convinced.

Some people in the office think Peyton's marketing power took a serious hit on Feb. 2nd -- and it could open the door for other players like Russell Wilson and Richard Sherman to swoop in on those coveted sports-oriented endorsements.

Then again, no one rocks a pair of stunner shades like #18.