Frederick made his AFL debut for Fremantle during round seven of the 2020 AFL season in the Western Derby at Optus Stadium kicking a goal on debut.[5] Frederick finished his debut year having played 10 games and kicked four goals.[6]
Frederick had a stand out performance during round 11 of the 2022 AFL season, he kicked two goals and finished with a game-high 11 score involvements, 17 disposals and four marks during Fremantle's 38 point win over Melbourne at the MCG.[7] Frederick again had a great performance the following week during Fremantle's top 4 clash against Brisbane, kicking 3 goals and amassing 18 disposals, 7 score involvements and 10 marks in the 14 point win.[8] Frederick was among Fremantle's best in round 17 during the 41 point win over St Kilda, kicking an equal game-high 3 goals.[9] Later that month Frederick was handed a one-match ban by Fremantle after consuming alcohol during a six-day break and as a result he missed Fremantle's round 13 game against Hawthorn.[10] Frederick finished 2022 having played 22 games and kicked 28 goals in a breakout season.
Frederick made a memorable impact during round 20 of the 2023 AFL season in Fremantle's 7 point win over Geelong at Kardinia Park, kicking an "unbelievable goal" at a crucial stage in the game to help win the match. Despite being labeled "one of the goals of the season" by Fox Sports journalist Mark Howard, it failed to receive the Goal of the Year nomination, with Taylor Walker of the Adelaide Crows instead controversially winning the nomination.[11][12]
Frederick made the line-up for Fremantle's opening game of the 2024 AFL season against the Brisbane Lions. He collected 15 disposals and kicked an impressive goal in the final quarter during the 23 point win.[13] He kicked two goals the next week against North Melbourne at Marvel Stadium.[14]
^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.