He represented South Australia in the 2009 AFL Under 18 Championships, in which he captained the side, received All-Australian honours and won the state most valuable player.

[3] He received mid-year honours in 2009 when he represented South Australia in the AFL Under 18 Championships, in addition to captaining the side.

[4] His performances in the championships saw him earn a spot in the All-Australian team as the ruck-rover[5] and win the most valuable player for South Australia.

[6] While completing year twelve, he played in the South Australian National Football League (SANFL) with the Sturt Football Club; he played the second half of the season with the senior side, which included a best on ground performance in the preliminary final against Glenelg—where he took a match-saving mark in defence[7]— and the grand final loss to Central District.

[16] In his fifth match, he received the round five nomination for the AFL Rising Star after he recorded twenty-four disposals, six marks, four tackles and two goals in the fifty point win against the Brisbane Lions at the Melbourne Cricket Ground.

[21] He was considered one of the early favourites to win the rising star in the betting markets,[22] and ultimately finished fourth overall in the award.

[26] Many players, commentators and coaches spoke out against the suspension, including several Melbourne teammates who were later fined for voicing their disapproval via Twitter.

[29] Throughout the year, teammate Tom Scully was linked to a move to incoming team, Greater Western Sydney,[30] which created the debate of whether Trengove or Scully added move value to Melbourne, with Herald Sun journalist, Mark Stevens, noting Trengove had more worth due to his leadership qualities.

[40] A reduction in fitness due to the foot injury and Melbourne having one of its poorest seasons in history saw Trengove's form drop.

[47] During the trade period, the Herald Sun reported that he was linked to Richmond in exchange for pick twelve in the 2014 national draft.

[51] There was uncertainty surrounding his 2015 season and whether he could make a return,[52] before he confirmed to Melbourne radio station, Triple M, in April 2015 that he was not going to play at all in 2015 and would instead focus on 2016.

[55] After strong form in the VFL,[56][57] he made his long-awaited return to AFL football in the eighteen point loss against Hawthorn at the Melbourne Cricket Ground in round eleven,[58] in which he recorded nineteen disposals and four clearances.

[65] He was promoted to the senior side for the round eighteen match against Port Adelaide at the Melbourne Cricket Ground and his return was labelled as one of the AFL's "feel-good stories" by The Age journalist, Jon Pierik.