WASHINGTON: Reigning US Open champion Emma Raducanu of Britain advanced to the quarter-finals of the ATP and WTA Washington Open, refusing to wilt Thursday after a marathon match in sweltering heat. The English 19-year-old outlasted Colombia’s Camila Osorio 7-6 (7/5), 7-6 (7/4) after two hours and 50 minutes for a gritty victory in the WTA’s longest two-set main draw match of the year. “It has got to be one of the most physical matches I’ve ever played,” Raducanu said. “It was a pretty monumental effort to really get through that. “I’m just really pleased and proud of how I dug in when it really mattered. It just gives you a lot of confidence coming through a match like that. “Physically, I’m pretty pleased with how I held up in that match. Looking forward to going again.” Raducanu advanced to a Friday quarter-final against Liudmila Samsonova, who rallied past Australian Ajla Tomljanovic 4-6, 6-3, 6-2 at the US Open tuneup. It will be only Raducanu’s third quarter-final since her amazing Grand Slam title run last year at New York, having reached the last eight at Cluj-Napoca last October and Stuttgart in April. She has yet to reach a semi-final since taking the trophy last September at Flushing Meadows.