Not long ago Petr was a celebrated and well-paid footballer, a national team player, now he is trying to restart his career in a small regional club. His biggest rival, however, has long been not his opponents, but his own weaknesses - first and foremost his addiction to slot machines. The story takes place over the course of a single day and gives a glimpse into the mind of Petr, a footballer with a god-given talent, but who has to start from scratch because his addiction has robbed him of everything. His main, and in fact only, support is his coach, who moves Petr into his home, takes care of his money and keeps an eye on him to prevent him from playing. While Petr is quite successful on the field, in the moments when he has nothing to do, he is overwhelmed by his current biggest rival - "roaming" - the insistent, compulsive fantasy of playing and winning at the slots.

Opponent is loosely inspired by the fate of Milan Pacanda, a once-great football player who was overcome by an addiction to slot machines. Pacanda made several attempts to restart his career at smaller clubs, but despite his initial determination, his vices always caught up with him. In his film, however, Ondřej tells the story not of a footballer, but of a man. The basic starting point, from which not only the script but also the audiovisual form of the film was derived, is the need to let the viewer look inside the character, into his fears and to allow the audience to experience that carousel of constantly recurring insistent fantasies that force a person to succumb again and again to the object of addiction. For this reason, the film is told subjectively, from the protagonist's point of view.