Fritz and Tiafoe advance to all-American semis NBC Bay Area [Video]

Day 9 of the U.S. Open tennis tournament in Flushing Meadows, New York marked the start of quarterfinal action in men’s and women’s singles.

Frances Tiafoe has reached the U.S. Open semifinals for the second time in three years when his quarterfinal opponent, Grigor Dimitrov, stopped playing because of an injury in the fourth set. Tiafoe was leading 6-3, 7-6 (5), 6-3, 4-1 Tuesday night when Dimitrov retired from the match. Tiafoe advances to an all-American semifinal against Taylor Fritz, guaranteeing the United States a representative in the men’s final. Fritz eliminated No. 4 Alexander Zverev in four sets earlier Tuesday to get to a Grand Slam semifinal for the first time.

Emma Navarrohas reached her first Grand Slam semifinal by beating Paula Badosa 6-2, 7-5 at the U.S. Open. Navarro is a No. 13-seeded American who had never even won a match in the main draw of her home major before this year. She advanced to face No. …