Adam Vinatieri -- Superstar Kicker EATS IT HARD ... During Field Goal Attempt

He's usually flawless under pressure, but future Hall-of-Fame kicker Adam Vinatieri WENT DOWN like a sack of potatoes during a field goal kick in NYC yesterday.

The Indianapolis Colts player was a Super Bowl event where he was supposed to put one through the uprights for a bunch of excited fans ... but when he went to plant his foot, things took a turn.

Of course, Adam got up like a champ ... and don't worry, he still made the kick.