Theodoridis started his career at the academies of AEK Athens and was promoted to the men's team in 1969 with the renewal of roster attempted by the then coach, Branko Stanković. He was a central defender unusual for the time, since he was good with the ball at his feet and had good positioning, resulting playing also as a right back.
Theodoridis began his career at the academies of AEK Athens, being elevated to the men's team in 1969 following a roster renewal led by coach Branko Stanković. He was an exceptional central defender due to his ability with the ball and positional awareness, which also allowed him to play as a right back.