The first player Adelaide signed through the AFL NSW scholarship scheme, Walker was 17 when he kicked seven goals and won best afield in a North Broken Hill premiership. He captained the Crows from 2015 to 2018 and was named the AFLPA's best captain in 2016 and 2017. He became the club's all-time leading goalkicker with his 441st in Round 18, 2020, and marked his 250th game in 2023 with 10 goals against West Coast. He retired at the end of the 2026 season, having played 319 games and kicked 715 goals.