Well, one play can make a difference. Happens all the time.
If Beux Limmer doesn't miss a block last year in the playoffs the Rams likley beat Philly. That doesn't mean he made the only play that was determinant in that game, but if he makes that block the Rams likley go up 29-28 with less than a minute left.
If Williams doesn't fumble the ball, the Rams likley sweep the Niners and win the division. That Atlanta game becomes important and they handle their business.
So yes, there are many plays in a season, but there are plays that become turning points and that was a huge turning point this year. We all kind of knew it could bite them in the ass at the time, and it did.