The 20-year-old's exit means Serena Williams remains the last woman to successfully defend the US Open title back in 2014.
Coco Gauff survived late-match drama to keep her US Open title defence alive with a 3-6, 6-3, 6-3 victory over Elina Svitolina on Friday.
Gauff, seeded third, fired 10 aces and needed just 66 minutes to beat 66th-ranked Gracheva. She saved eight break points -- including two with aces in the final game
Gauff was not the only big name going out, as Rybakina crashed to a 3-6 7-6(3) 6-4 defeat by former US Open runner-up Leylah Fernandez.
Tearful Coco Gauff was dumped out of the Olympics Games tennis tournament on Tuesday in a stormy defeat to impressive Donna Vekic of Croatia.
The world number one is just one match away from becoming the first woman to win the tournament in three straight years since Justine Henin in 2007 after a 6-2, 6-4 victory.
World number three Coco Gauff came back from a set down to defeat Ons Jabeur and reach her second French Open semi-final on Tuesday.
Gauff has been outspoken from a young age, and grew up with activism engrained in her DNA, passed on from her grandmother Yvonee Lee Odom, who desegregated her high school in Delray Beach in the early 1960s.
Formidable world number two Aryna Sabalenka blasted past Coco Gauff into the Australian Open final on Thursday to keep her title defence on track.
Swiatek blitzed 80th-ranked Wang Xinyu of China 6-0, 6-0 on the back of 21 winners as the 22-year-old Pole took another step closer to becoming the first woman since Justine Henin in 2007 to win back-to-back titles at Roland Garros.
World number eight Daria Kasatkina has given the thumbs down to the idea of "trash-talking" between professional tennis players, saying that disparaging or boastful comments under the guise of banter would not work well in an "intelligent" sport.
World number one Iga Swiatek is the favourite to win an Australian Open women's draw shorn of some of its biggest recent stars.
French Open women's champion Iga Swiatek said she was "overwhelmed" after finding out Poland and Bayern Munich striker Robert Lewandowski was in attendance to witness her claim a second Grand Slam title on the Parisian clay.
Iga Swiatek romped into her second French Open final on Thursday and will face Coco Gauff for the title after the teenager became the youngest Grand Slam finalist since 2004.
