West Ham's 17-match unbeaten European run came to an end on Thursday with a 2-1 loss away to Olympiakos, while Rangers battled for a point in a goalless Europa League draw at Sparta Prague.
Kostas Fortounis struck from distance to give the Greek side the lead and Rodinei added a second before half-time with a deflected effort.
Lucas Paqueta volleyed in late consolation for the Hammers, who remain top of Group A on six points from three matches. Freiburg are level after a 3-1 victory over Serbia's Backa Topola.
Rangers relied on a fine display from goalkeeper Jack Butland in a 0-0 stalemate in the Czech Republic. They are third in Group C, led by Real Betis who won 1-0 away to Aris Limassol thanks to an Ayoze Perez goal.
Marseille picked up their first victory of the competition, beating AEK Athens 3-1.
Orbelin Pineda cancelled out Vitinha's opener for Marseille, but a moment of madness from AEK goalkeeper Cican Stankovic cost his team dearly.
Stankovic hit a pass right to Vitinha and then wrestled the Portuguese forward to the ground, conceding a penalty and earning himself a red card.
Amine Harit converted the spot-kick before Jordan Veretout tucked away another penalty for Gennaro Gattuso's side as they moved top of Group B. Brighton host struggling Ajax in the other game.
Colombia international Luis Muriel netted both goals for Atalanta in a 2-2 draw at Austria's Sturm Graz in Group D.
Sporting played most of their 1-1 draw against Polish champions Rakow Czestochowa a man down after Viktor Gyokeres was sent off.
Liverpool take on Toulouse later chasing a third successive win in Group E.
In the Europa Conference League, in-form Aston Villa eased to a 4-1 win at Dutch high-flyers AZ Alkmaar.
Leon Bailey and Youri Tielemans gave Villa a two-goal lead in the first half against a side who have dropped just two points in the Eredivisie this season.
Ollie Watkins and John McGinn put the game out of reach before Ibrahim Sadiq pulled one back.
