Maroussi basketball club caused a major upset in the A1 league’s quarterfinal best-of-three playoffs by defeating Aris last night, away for the second time in their series, to reach the semifinals. Maroussi, which stunned Aris at its Thessaloniki base in the opening game but then lost in Athens, repeated its on-the-road feat in last night’s decider with an 85-79 score to snatch a semifinal spot. The visitors were in command throughout the game and led at the end of all four terms (19-24, 40-44, 56-67, 79-85). Aris’s failure to reach the semifinals served to highlight the continuing demise of basketball in Thessaloniki, once a Greek and European power. All four semifinalists are based in Athens. Maroussi’s triumph pits the Athens club against Olympiakos in the semifinals, but the latter has the home-ground advantage. The semifinals, best-of-five encounters, begin tomorrow and continue next Tuesday. In the other semifinal, Panathinaikos greets Panionios in the opening game. Should Panathinaikos and Olympiakos, the favorites in their respective semifinals, make the final, Panionios will have the home advantage in the best-of-five series against Maroussi for third place and a Euroleague spot. Maroussi have previously played in league finals but never in the Euroleague. Should the Athens team capture third spot in the domestic A1 league, it is unclear whether Maroussi meets various standards set by the European club-level competition’s organizer, including stadium quality and number of fans.