West Ham United dropped points for the first time in this season's Europa League campaign as a late own goal by Tomas Soucek in a 2-2 draw at Genk denied them a fourth successive win in Group H on Thursday.
It looked as though Said Benrahma's second-half brace had secured the Hammers a last-16 spot with two games remaining but Soucek's attempted clearing header flew past Alphonse Areola in the 87th minute.
The London club still look almost certain to continue their European campaign in the new year as they lead the standings with 10 points from four games.
Genk have four points with Rapid Vienna and Dinamo Zagreb, who play later, both on three. A win for either Rapid or Dinamo would send West Ham into the knockout phase.
This season's Europa League has been revamped with the eight group winners moving through automatically to the last 16 while the eight runners-up will go into a playoff round with the teams finishing third in their Champions League groups.
West Ham have been enjoying a remarkable campaign under David Moyes but his 1,000th game as a manager did not start well as Genk took the lead in the fourth minute when Joseph Paintsil slotted home at the far post.
The visitors, fourth in the Premier League, were off the pace in the first half but were far better in the second and Benrahma equalised with a clinical finish from a pass cut back across the area by Vladimir Coufal.
Algerian Benrahma then produced a superb solo effort in the 82nd minute, jinking through the Genk defence before poking a shot into the net.
Genk were handed a reprieve, however, when Soucek's diving clearance skimmed off his head and the ball flew into his own goal.