[2][1] In 2018, Deng was controversially selected to compete in 800 m at the 2018 Commonwealth Games, Gold Coast, Queensland having not qualifying for the final at the Australian Athletics Championships.
In July 2018, at the IAAF Diamond League meeting in Monaco, he finished seventh in the 800 m but broke the Australian record with a time of 1:44.21.
The previous Australian record of 1:44.30 was set by Ralph Doubell in winning the gold medal at altitude at the 1968 Mexico Olympics and equalled in 2014 by Alexander Rowe in Monaco.
[4] Following the political controversy surrounding purported "African crime gangs" in Melbourne, Deng was cited by the ABC as "a track star of boundless potential" and "proof positive of what immigrants can offer to their adopted country when given the opportunity.
"[5] In 2023, Deng recaptured the 800 m national record (which had been progressively improved by his training partner Peter Bol in 2021 and 2022) with a new personal best of 1:43.99 in Lyon, France.