Amnat Ruenroeng, the man who upset the Zou Shiming apple cart last year and firmly established himself as one of the world's best flyweights, suffered the first loss of his career earlier today as former victim John Riel Casimero put him down with a wicked body shot.

Here's the final round for those interested.

Ruenroeng (17-1, 5 KO) had defended his IBF title, taken from Rocky Fuentes in 2014, five times against the likes of Kazuto Ioka, McWilliams Arroyo, and the aforementioned Shiming. Four rounds into the rematch with Casimero (22-3, 14 KO), as things started to get a bit chippy, Ruenroeng ran headlong into a check hook that sent him to his knees.

Ruenroeng clinched his way back into the fight, only to get leveled by a liver shot that put him down for good.

Does Casimero stand a chance against the likes of Roman Gonzalez and Juan Francisco Estrada? Probably not, but this is a major win for the young Filipino.