Greek champions Olympiakos Piraeus and runners-up AEK Athens enter the Champions League competition tonight in an effort to advance to the next qualifying round of Europe’s most prestigious football tournament. The reds will travel to Belgrade, Serbia to face dangerous Serbian team Partizan Belgrade (9.45pm), while AEK will have a difficult task hosting favourites CSKA Moscow at the OAKA Olympic stadium (8.30pm). The return leg of their matches is scheduled for August 1.