Canadian teen Leylah Fernandez never stopped believing she could beat Naomi Osaka, not even when the four-time Grand Slam champion was serving for the match, and her determination was rewarded.

Three days before her 19th birthday, the 73rd-ranked daughter of an Ecuadoran father and Filipino-Canadian mother battled back to deliver a stunning 5-7, 7-6 (7/2), 6-4 upset of the world number three from Japan.