Olympiakos Piraeus beat Aris 1-0 to extend their lead in the Greek Super League as Panathinaikos crashed to a 1-0 defeat at AEK.
League leaders Olympiakos hosted Aris and the match had been under way for just over a minute when Spaniard Albert Riera handed the home side a very early lead.
Olympiakos held on to that advantage to earn their sixth victory in seven games.
Second-placed Panathinaikos suffered their first defeat of the season, losing 1-0 at AEK in the Greek capital.
The only goal in this game came from Rafik Djebbour after just four minutes.
Olympiakos are now four points ahead of Panathinaikos, and AEK are now in third place at another point.