[5] He played there for two seasons, but decided to transfer schools after the soccer coaching staff was relieved of their duties.

[5] He served as an unused substitute keeper for Durham United FC for a match in League1 Ontario in 2014, but did not play.

[9][10] In March 2016, Giantsopoulos joined Devonport City in the NPL Tasmania, the second tier of soccer in Australia.

[12] In the 90th minute of the Round of 16 match in the FFA Cup against Bentleigh Greens with the score at 0-0, he suffered a shoulder injury and was forced to leave the game, which Devonport ultimately lost 1-0, after extra time.

[16] In 2017, he joined Broadmeadow Magic in the NPL Northern NSW, a different regional league in the same second tier of Australian soccer.

[19] On August 18, in a match against South Hobart, as a penalty shot was about to be taken, Giantsopoulos ran up and kicked the ball away before it could be taken.

[19] Giantsopoulos returned to Canada and signed with Cavalry FC of the Canadian Premier League on January 23, 2019.

[27][28] In his limited playing time for Cavalry, Giantsopoulos earned four clean sheets and had the best save percentage of any CPL goalkeeper.

[40] After the 2023 season, he turned down a contract extension offer from York,[41] and he began training with his former club Cavalry, but did not ultimately sign.