How exactly? Let’s take a look:
The background
At the end of the second quarter, USC and Northwestern were tied at 14. The Trojans’ defense had allowed touchdowns on two of the Wildcats’ first three drives, and Northwestern was ready to get the ball back early in the second half.
the choice
USC quarterback Jayden Maiava threw a bad interception deep in his own territory. Northwestern defensive lineman Najee Story headed to the goal line for a pick six that would have left the Trojans down seven.
the loose ball
It must be recognized that Maiava did not abandon the play. Instead, he chased Story and hit him just as he was preparing to cross the goal line. Story fumbled through the end zone and out of bounds, giving the ball back to the Trojans with a touchback at the 20-yard line.
The alternative ending
If Story scores on the play, Northwestern takes a 21-14 lead. Since the Wildcats also received the ball early in the second half, the Trojans were in danger of losing by multiple scores.
The real ending
Instead, the Trojans got the ball back and immediately scored a touchdown on their next drive. USC outscored Northwestern 24-3 the rest of the game as the Trojans cruised to a comfortable victory.
We don’t know what would have happened if Story had scored on that interception. But it doesn’t seem like a stretch to say that one play totally changed the trajectory and momentum of the game.