Manchester United have to wait to secure their place in the Champions League knockout stages after Basel capitalised on a stark second-half drop off by Jose Mourinho's men.
Starting Group A with four wins from as many games put the Red Devils on the brink of the last-16, although the end of their 100 per cent record has prolonged the wait for what surely remains inevitable progress.
Michael Lang's late effort secured Basel a deserved 1-0 win after a second-half onslaught that followed a dominant opening period by the visitors, with Anthony Martial and Marcos Rojo hitting the frame of the goal.
The result left Mourinho somewhat confused about the permutations, but avoiding a record European defeat at home to CSKA Moscow will ensure progress.
A point will see them top Group A, just as it would have done in Basel - a fact that caught United in two minds about whether to settle for a point or go for victory.
"We played against a team that played with five defenders," Mourinho said. "We knew that.
"We tried to play with three attacking players and that worked in the first half because they couldn't handle us.
"We didn't score in the second half probably (because of) the fact that we know one point is enough.
"So it's hard for me to be upset with the players. The first half the attitude was good, the football was good.
"It is really difficult to blame. It's just football."
Mourinho said it "should have been 5-0" in the first half.
Despite making seven changes, United dominated in the opening period on the relaid St Jakob-Park turf as Paul Pogba, captaining the side for the second time, pulled the strings.
It was just his second appearance since he sustained a hamstring injury when the sides met on matchday one at Old Trafford, and his second-half substitution in Switzerland made a telling impact.
"The first half was a perfect half - without the goals," Mourinho said. "It was difficult to repeat in the second half. We knew that the opponent would try a different reaction.
"Did Paul Pogba coming out have an impact on the team? I think it had an impact.
"We were not such a good team after Paul came out, but he had to be (substituted). He cannot go to levels of fatigue after 65 minutes.
"But I brought to the pitch an experienced player like (Nemanja) Matic and I thought he could affect the game.
"I bring Marcus (Rashford) to give us more depth, more speed, more problems to them, Zlatan (Ibrahimovic) to hold the ball, drop and have it.
"The approach was good, I cannot blame the players.
"I think we play a match like this 10 times and nine we win comfortably.One we lose and the one was now."