Sports Australian Open: American Frances Tiafoe notches emotional upset of Grigor Dimitrov January 20, 2019Sandra Harwitt, Special for USA TODAY SportsComments Off on Australian Open: American Frances Tiafoe notches emotional upset of Grigor Dimitrov Frances Tiafoe celebrated his 21st birthday with the biggest win of his career, knocking off Grigor Dimitrov to reach the quarterfinals in Melbourne.