Giustino has a career-high ATP singles ranking of 127 achieved on 12 August 2019 and a career-high ATP doubles ranking of 311 achieved on 15 April 2019. Giustino made his ATP main draw debut at the 2015 BRD Năstase Țiriac Trophy, where he qualified for the main draw.
Jason Murray Kubler (/ˈkuːblər/ KOOB-lər; born 19 May 1993) is a professional tennis player from Australia. A former world number one junior, Kubler was often referred to as a “right-handed version of Rafael Nadal” for his powerful build and strong forehand. Kubler was born in Brisbane, Australia to an Australian father and a Philippines-born mother. His father, John, introduced Kubler to tennis at the age of five, but died from cancer when Kubler was eight years of age. Jason Kubler grew up in the north Brisbane suburb of Mango Hill with an older brother and a younger sister.