Ajax came from behind to rescue a Champions League point at Benfica, during a Group E match marred by violence in the stands.
Police and supporters clashed in the away end at the Estadio da Luz, where former Southampton striker Dusan Tadic cancelled out Goncalves Oliveira’s opener.
Ajax could have progressed to the knockout stages had they won.
The Dutch side travel to Athens to face AEK Athens in their next match on 27 November, knowing a victory will take them through.
Benfica still stand an outside chance of progression, but they will need to win both games and hope Ajax drop five or more points in their remaining two fixtures.
Robert Lewandowski’s two goals saw Bayern Munich beat AEK Athens 2-0 to all but seal their progress to the knockout stages – the German champions need just a point from their next match.
Elsewhere, Hoffenheim came from two goals down to draw level in the 92nd minute at Lyon as the Frenchmen lost ground on Manchester City in Group F.
Valencia claimed their first victory of the campaign with a 3-1 win over Young Boys courtesy of goals by Mina Lorenzo and Carlos Soler in Group H’s early kick-off.
Roma beat CSKA Moscow 2-1 as the Italian side continue to keep pace with holders Real Madrid in Group G.