Treloar was recruited by as an under-age selection prior to the 2010 AFL draft and played with the Dandenong Stingrays and the Noble Park Football Club during his junior career. He made his AFL debut in round 3, 2012 against at Blacktown International Sportspark. He was the round nomination for the Rising Star after the round 18, 120-point loss to, where he amassed 39 disposals. He went on to finish fourth overall in the award after receiving 15 out of a possible 45 votes. Treloar played 20 games during 2013, averaging 24 disposals a match, and finished fifth in the best-and-fairest count. He was touted by former forward Dermott Brereton as the next Mark Ricciuto, saying that he had the potential to "be an absolute elite player in the midfield and be top five in the comp with his ability, with his skill set and with his want and desire for the game." His 2014 season was described as "brilliant" where he averaged 27.6 disposals and 5.5 tackles in 20 matches and finished fourth in the best-and-fairest count. He was recognised as one of the best young players in the league by being selected on the wing in the AFLPA 22under22 team. Treloar had his best season to date during 2015 where he was the runner-up in the best-and-fairest, finishing behind Heath Shaw, however, his season was filled with speculation that he would leave the Giants to return to his home state of Victoria. He informed the club in September that he wanted to be traded and nominated Collingwood as his preferred destination.
Collingwood (2016–present)
Treloar officially joined Collingwood on a six-year deal on 21 October 2015. He had an outstanding first season for the club, playing all 22 games, and lead the club for disposals, tackles, clearances, inside 50s and bounces. At the end of the season he won the R.T. Rush Trophy, finishing second in the Copeland Trophy count, behind skipper Scott Pendlebury. Treloar followed up with a consistent second season at the club in 2017, playing in 21 games. In 2018, Treloar won the Anzac Medal, and later played in the losing grand final to West Coast. Treloar's 2019 season saw him win plenty of the football, he finished the season with a total of 789 disposals which saw him lead the entire AFL in the home and away season, as well as finals, he also did lead the league in handballs, tallying 454 for the season. His season was highlighted with 40 disposals and 7 tackles against North Melbourne in Round 15, he averaged 32.9 disposals per game, played 24 games and polled 18 Brownlow Medal Votes. He was awarded the Jock McHale Trophy for finishing fourth in the 2019 Copeland Trophy vote count.
