Despite two goals and another encouraging display from Rasmus Hojlund, United continue to labour defensively and goalkeeper Andre Onana made a second mistake in as many European appearances for the club.
Having twice let a lead slip, the stopper played a poor ball into midfield and allowed Dries Mertens to latch onto it, with Casemiro conceding a penalty and being sent off for a second booking when trying to cover.
While Mauro Icardi missed the spot-kick, the Argentine forward put the Turkish giants into the lead with only minutes to play with a delightful dink over Onana following yet more lapses in concentration from the home side.
Ten Hag’s have now been beaten six times in ten games across all competitions and the home form that took them a victorious League Cup final and Champions League qualification last season appears to have evaded them entirely.
Still, the Dutchman vowed his team remain united despite a bleak start to the season, both on and off the pitch.
"The mental errors we make, you cannot allow them at this level,” he said.
“You get punished. This is difficult to control. We are all in this together. We were twice up and in control of the game. We expect more together."