Panathinaikos lost ground in its battle to earn the second spot, behind Barcelona, in its Euroleague group after going down 77-75 at Armani Milano on Thursday.
The Greens suffered their fourth loss in eight games, but have retained a superior head-to-head record with the Italian team having beaten it by 16 points at home in January.
A disappointing first half for Panathinaikos saw it score just 26 points, but the Greeks nearly made amends in the second when they notched up 49.
Armani was on top for the whole of the game at the court where Olympiakos went down by 30 points last month. Dimitris Diamantidis and Stephane Lasme were poor on the night, leaving it to James Gist and debutant Zach Wright to pose a challenge to the host in Milan.
The first half ended with Armani leading 41-26, and Panathinaikos played catch-up in the second. It managed to reduce the arrears and even threatened to snatch victory in the very end when it reduced the deficit to just one point (76-75) with 4.5 seconds left.
However a free throw by Keith Langford three seconds from the end and a missed shot by Wright sealed victory for the Italians.
Gist was impressive with 21 points and nine rebounds, seconded by Wright who scored 17 points for Panathinaikos.