In 2019, he was selected for the New South Wales Under-18's team after an impressive year where he won the 2019 S. G. Ball Cup with the Illawarra Steelers as captain.

[2] Sullivan made five appearances for St. George Illawarra in the 2021 NRL season as the club missed out on the finals by finishing 11th on the table.

[3] Sullivan played nine games for St. George Illawarra in the 2022 NRL season as the club finished 10th on the table and missed the finals.

[6] On 17 August 2023, Sullivan was released from the final years of his contract to sign with the Wests Tigers on a four-year deal.

[7] Sullivan played nine games for the Wests Tigers throughout the 2024 NRL season as the club finished with the Wooden Spoon for a third consecutive year.