Rivers debuted in the Demons' one-point win over the Carlton Blues in the second round of the 2020 AFL season.[9] He collected 12 disposals, 3 marks and 2 tackles.[10] Rivers signed a contract extension in October 2020, keeping him at the club until 2023.[11] Josh Mahoney, Melbourne's then general manager of football, stated "Trent has already shown signs of what he’s capable of and we couldn’t have asked more from him this season. We look forward to his continued development over the next three years."[11]
Rivers earned a Rising star nomination in round 11 of the 2021 AFL season, after collecting 19 disposals, seven intercepts and 326 metres gained.[12]
^The 2020 season was played with 17 home-and-away matches per team (down from 22) and 16-minute quarters with time on (down from 20-minute quarters with time on) due to the impact of the COVID-19 pandemic.
^2023 statistics include one game in which Rivers was substituted out of the game (round 6) and was replaced by Bailey Laurie.