Manchester United equipped a defense without Victor Nilsson Lindelöf - a defense that forgot how to defend with a quarter played.
Then former Chelsea player Demba Ba ran away in a free position and with all the time in the world he placed 1-0 for the home team Istanbul Basaksehir.
40 stood on the clock when Edin Visca stayed ahead and thundered in 2-0, before Anthony Martial immediately reduced with a well-aimed nod.
Five changes were not enough
In the second half, United made five substitutions - including Paul Pogba, Mason Greenwood and Edinson Cavani - to besiege the Turks' penalty area.
In extra time, the English were extremely close to making it 2-2 via an own goal, but the ball was cleared at the last minute and 2-1 the match stood out.
Basaksehir can thus celebrate the club's first goal and first point ever in the Champions League.
United leads the group by six points.