Ramkumar Ramanathan, ranked 222 in the world, upset world No. 8 and top seed Dominic Thiem in straight sets, 6-3 6-2, to enter the quarterfinals of the Antalya Open in Turkey. This is Ramanathan’s biggest win till date.
Let us dig who are all have defeated world top rankers
Sania Mirza (the then No.27) has notable wins over Svetlana Kuznetsova, Nadia Petro and the former World No. 1s Martina Hingis, Dinara Safina, and Victoria Azarenka in 2006. Though she has not won any major singles titles, Sania Mirza has won Grand Slam titles in women doubles and mixed doubles.
Leander Paes defeated Pete Sampras (the then World No.2) 6-3, 6-4 at the New Haven ATP tournament in 1998. In 1997, he made his best singles performance in a Grand Slam, getting to the third round of the US Open, beating Carlos Costa and Arnaud Boetsch. In the Davis Cup, his major wins came against French duo of Arnaud Boetsch and Henri Leconte in 1993, Wayne Ferreira in 1994, and Goran Ivanišević in 1995.
Ramesh Krishnan defeated the then World No. 1, Mats Wilander in the 1989 Australian Open. . In Davis Cup matches, he had many surprising victories over John Fitzgerald and Wally Masur in 1987.
In the 2009 Chennai Open, Somdev Devvarman (84) defeated Carlos Moya (the then 42) and Ivo Karlovic (the then 25). In the Legg Mason Tennis Classic, he defeated Marin Cilic. In 2011, at the ATP Masters 1000, he defeated Marcos Baghdatis (the then No.22) and moved to World No.73. At the Sony Ericsson Miami Masters ATP 1000 tournament in 2011, he defeated Milos Raonic (No.34). At the Serbia Open in 2011, he avenged his US Open defeat by defeating Guillermo Garcia-Lopez. He made his Davis Cup debut in 2008. He has defeated Janko Tipsarevic in his Davis Cup tenure.
In the 2014 Chennai Open, Yuki Bhambri defeated Pablo Carreno Busta in the first round. He then got past Fabio Fognini in the next round.
