This has gotta hurt ...
Oakland Raiders QB Derek Carr -- a guy who has a rocket for an arm -- was running passing drills with some friends yesterday when he asked a friend to post up with a camera for a cool, action shot.
The plan was ... the photog stands roughly 15 yards downfield and Carr fires a football right at his face -- with a wide receiver set to race in front at the last second to make the grab.
Very cool, artsy, action shot.
Problem was ... something went wrong during the first take and the camera guy got ROCKED.
Don't worry, the guy couldn't have been hurt too bad ... 'cause they did a second take -- this time, it worked like a charm.
Check out the clip ... and try not to flinch.