They now lie second in the group on the same points as CSKA Moscow - against whom United need to avoid a six-goal defeat to be certain of finishing top.
Mourinho will be especially frustrated by the defeat because it means he can not afford to rest players against CSKA, just days before the Manchester derby.
For Manchester United both Zlatan Ibrahimovic and Paul Pogba came back from injury and were on United team that beat Newcastle United 4-1 at the weekend and are in line to play some part against Basel.
Despite that Southgate decided against picking him for an ultimately weak squad for the draws against Germany and the Brazilian's, there are a only few months to impress ahead of World Cup in Russian Federation this Summer but Smalling stated that he will be looking to give Southgate "no choice" but to pick him. Basel rode the storm, came back in the second half and showed great character.More news: Did Kris Jenner Confirm Kylie Jenner And Khloe Kardashian's Pregnancies?
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12' - Lovely ball from Pogba, slipping Lukaku in, and he holds off his man brilliantly, but then takes a touch too many and ends up bashing a finish to the side of Vaclik when he was close enough to block; a Peter Beardsley lift was what was really in order.
Suddenly unable to find any rhythm, United rode their luck again as Renato Steffen's powerful effort was narrowly off-target. Lang struck the bar with a 65th-minute header and United goalkeeper Sergio Romero made a series of diving saves.
Jose Mourinho has confirmed Zlatan Ibrahimovic, who is yet to score following his return from injury will be on the bench for the Red Devils.
With United appealing in vain for offside, Raoul Petretta's measured pass found Lang and he tapped in at the far post to leave Mourinho cursing.
In the final round on December 5, Basel plays at last-place Benfica, which has lost five straight, and Man United hosts CSKA.