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.