Spoiler alert: Which also-rans should contending teams fear?

As the calendar nears September, teams and fans of contenders begin circling dates and games on the schedule. Head-to-head matchups against other clubs vying for a playoff spot loom large, but the other games against also-rans can't be ignored. How teams fare against clubs out of the race can determine a playoff berth nearly as easily as the games versus other contenders. There are a few dangerous clubs primed to play spoiler down the stretch. Let's get into those ballclubs that are poised to upset other teams' postseason dreams, as well as the contenders who could be most affected.