Basel shocked Manchester United with a late winner to ensure Jose Mourinho's side still need a result in gameweek six to qualify for the Champions League last-16.
Jose Mourinho made a number of changes to his starting XI for the visit to Switzerland with United needing just a point to ensure top spot in Group A.
Marcos Rojo - back for the first time after a serious knee injury - struck the bar with a deflected shot from range, but Michael Lang turned home a late cross to hand the Swiss side a famous win
Lang arrived at the far post to slot in a low shot from fellow wing-back Raoul Petretta's pass across the goalmouth.
United still lead the group with 12 points, three clear of both Basel and CSKA Moscow, who earlier won 2-0 at home to last-placed Benfica.
Mourinho's men were made to pay for a wasteful first half when they were in control without ever hitting top form.
Needing only one point to ensure victory in the group, United twice struck the woodwork of Basel's goal late in the first half through a Marouane Fellaini header and Rojo's shot.
But a passive start to the second period let Basel seize control. Lang struck the bar with a 65th-minute header, and United goalkeeper Sergio Romero made a series of diving saves before Lang scored the late winner.
In the final gameweek on December 5, Basel play Benfica and United host CSKA.
Additional reporting by the Associated Press.
