The Opponent takes a look at the hardscrabble world of boxing from the perspective of a small-time boxing gym owner, the seen-it-all-and-then-some Tremont "Tre" Billiford, and a young up-and-comer, the charismatic and fast-moving Donell Fuseles. 

Beginning with an ad-hoc training session between the two, Donell seeks motivation, reps and inspiration from Tre for his upcoming fight with rising star Jas Dennis. As Tre and Donell trade barbs, insight and jabs, Donell shows his supreme confidence in his abilities as Tre attempts to keep Donell's sights on the fight and not on Donell's dreams of a lavish career. Donell reacts with frustration toward Tre, dumping his worry and anger at the trainer's feet and insulting both Tre's decaying gym and Tre's own decision-making. 

Trying to ignore their mutual concern about the fight with Jas Dennis, both rise to the occasion as Tre finally finds a way to channel Donell's fear and frenetic energy as he assures Donell he'll see him later that night after his big win. 

Time shifts forward five years, and the fight with Jas Dennis is now (seemingly) buried in the past. Tre's mental ability has begun to crumble as his own former time in the ring begins to take its toll, and Donell, showing up unannounced, starts to question Tre's advice given to him five years previously. Difficult truths are revealed as questions of loyalty, dreams deferred and fractured losses become unearthed.

Tensions quickly rise between the two broken men as both accuse the other of causing the failures that define their lives while they approach the inevitable fight that will ultimately prove who truly is the champ.