Konstantinidis started his career at Iraklis in 1994,[1] where his very good performances with the club, attracted the interest of AEK Athens and Olympiacos.
The player negotiated in the last six months before the end of his contract his transfer to a team of his choice and he agreed with AEK.
But the president of Iraklis, Petros Theodoridis wanted to give him to Olympiacos, from whom he had an offer.
Finally, the two sides ended up in the courts and Konstantinidis was left out of the squad for a few months.
Konstantinidis was a member of Greece U21 team that reached the final of the 1998 UEFA European Under-21 Championship in Romania, where he played in all 3 games.