Trengove is a highly touted key position prospect who was widely tipped to be a top-10 selection in the 2008 AFL Draft before a severe hamstring injury and surgical complications caused him to slide to pick 22, where he was taken with Port's second round pick. He is aligned to SANFL club Port Adelaide Magpies having been taken at pick #5 in the SANFL Mini Draft, recently making his reserve team debut after recovering from his previous injury.
After a difficult climb back from his injury, Trengove made his AFL debut in the opening Round of the 2010 after playing in the 2010 NAB Cup. His defensive pressure was evident as he had 4 tackles. Trengove played in rounds one to four of the 2010 season as a tall defender and ruckman, but was omitted from the Power's round 5 clash against top-placed St Kilda. He returned to Power's AFL side in Round 7 when they defeated Essendon at Etihad Stadium. This was arguably Trengove's best match so far, as he collected 11 disposals, 8 hit-outs, 6 tackles, 1 goal and 3 marks (one of them with seconds to go which ensured the team's win). He backed up his efforts with another strong performance the following round, achieving a career high 12 hit-outs. In the Power's Round 20 clash against the West Coast Eagles, Trengove totaled a current career-high 23 disposals, along with a game-saving late game spoil, which earned him the Rising Star nomination for that round. His 2010 season was recognised with the Gavin Wanganeen Medal as the club's best player under the age of 21.
In 2011, Jackson played every game for the Power. Also in 2011, there was a lot of speculation that Trengove would leave the club and move back to his home state of Victoria because of the current on-field and off-field dramas that were unfolding with the Power. He later dismissed these rumors when he signed a 2-year contract with the Power on the Monday after Round 21. He along with Travis Boak were jointly crowned the John Cahill Medallist at seasons end, the first time that there had been a tie at the club's best and fairest award.