What is the fine-grained topic of the following text: The knockdown was one of the few bursts of action in the fight as the length of Mario Barrios (16-0, 8 KOs) continually frustrated Devis Boschiero (39-5-1, 21 KOs), a 34-year-old Italian who was making his U.S. debut. Only return the topic.
Boxing match between Mario Barrios and Devis Boschiero