The match was decided by a set-piece with Olympiakos central defender Tasos Avlonitis heading in his first Greek Super League goal from an Alejandro Dominguez free kick just before the hour mark.
The “Derby of the Eternal Rivals” failed to live up to the pre-match hype, with both teams playing overly cautious football.
The hosts missed a great chance to make it 2-0 when Panathinaikos' English keeper Luke Steele felled Kostas Mitroglou in the box in the 78th minute.
However, Steele redeemed himself by diving to his left and saving Mitroglou’s spot kick, while Anastasiou was sent to the stands for his over-zealous complaints.
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The result meant Olympiakos moved into second in the Super League, three points behind leaders PAOK Salonika.
It has been a hugely successful week for Michel’s team, who also beat Juventus 1-0 at home in their midweek Champions League group match.
Leaders PAOK recorded a convincing 4-1 home win over third-place Veria, inflicting only the second defeat of the season on their opponents.
Elsewhere, OFI Crete fans were left stunned after Gennaro Gattuso resigned as coach following a 3-2 home defeat by Asteras Tripolis.
The 36-year-old Italian World Cup winner lasted only seven matches before quitting, hitting out at both his players and the club’s bosses.
(Editing by Mark Meadows; mark.meadows@thomsonreuters.com; +44 20 7542 7933; Reuters Messaging:; mark.meadows.reuters.com@reuters.net)
