Well, that day finally came ... and let's just say Knox has to be wishing it didn't.
Give credit to Johnny for posting footage of the race to his 4 million Instagram followers ... 'cause he couldn't even last a second before he fell far behind, even though he brought his own cheerleaders for the event.
FYI -- Patillo is the top-ranked sprinter in her grade ... and has come in first at the AAU Junior Olympics and USATF National Junior Olympic Championships in the past. She's also gone viral on social media multiple times for showing off her insane speed.