As a teenager he was a talented cricket player, touring England with NSW youth teams.
[2][3] He fell into Greater Western Sydney Giants' recruitment zone in the Riverina and was briefly part of its academy, but in May 2016 the AFL ruled that Marshall had not spent enough time at the club and thus would have to go through the normal draft process rather than going straight to GWS as an academy player.
[6] He made his debut in the seventeen-point win over the Western Bulldogs at Mars Stadium in round twenty-two of the 2017 season.
[7] Todd Marshall was good friends with Patrick Ryder during his tenure at Port Adelaide and when the latter was traded to St Kilda at the end of the 2019 AFL season the former changed his guernsey number from 13 to 4.
[8] The 2022 season proved to be Marshall's best yet, playing in 21 of 22 games and kicking a career high 45 goals to be Port Adelaide's leading goalkicker.