Manchester United's miserable season continued with a 3-2 home defeat by Galatasaray as Casemiro was sent off giving away a penalty which Mauro Icardi missed before scoring the winner to leave the hosts bottom of Champions League Group A on Tuesday.
Looking to put a fourth Premier League defeat of the season against Crystal Palace on Saturday to the backs of their minds, United flew out of the traps in the Manchester rain, racing into a 17th-minute lead through Denmark striker Rasmus Hojlund.
Their advantage lasted less than six minutes however as Wilfried Zaha, playing against his former club, scooped home the equaliser after poor defending from the hosts.
After the break, Hojlund brilliantly capitalised on a slip from Galatasaray defender Davinson Sanchez to clip United back in front in the 67th minute, only for Kerem Akturkoglu to level four minutes later and stun Old Trafford into silence.
A mistake from United goalkeeper Andre Onana forced Brazilian midfielder Casemiro to conceded a penalty, which saw him sent off after receiving a second yellow card.
Icardi let United off the hook as he drilled his spot kick wide but the Argentine picked himself up and slotted home a fine winner nine minutes from time to send Galatasaray up to second in the group on four points and leave United pointless.
Bayern Munich are top on six points from two games after a 2-1 win at FC Copenhagen, who are third with one point.
"Our opponents are maybe not very successful on the outside but they are a good team," Galatasaray coach Okan Buruk said.
"We have beaten a huge opponent. It is a massive week for Turkish football and of course for us."
United coach Erik ten Hag added: "The mental errors we make, you cannot allow them at this level. 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."
Desperate United
Back in the Champions League after a one-year absence, United were desperate for three points after losing to Bayern in their opening Group A encounter, having suffered their worst start to a domestic league campaign since 1989-90.
In European competition, they were also out to avoid losing a third match in a row, which they had not done since 2012-13.
Hojlund's bullet header, from a pinpoint Marcus Rashford cross, could not have got the hosts off to a better start.
Former Crystal Palace winger Zaha, who only made four appearances for United between 2013-15, got revenge on the club who did not give him a proper chance, capitalising on hesitant defending from Diogo Dalot before finding the net.
After the break, Hojlund continued his European purple patch with a superb solo goal but, as was the case on three occasions during their opening group match in Munich, United conceded too quickly after scoring themselves as Akturkoglu struck.
At 2-2, the home supporters still believed their team could find the winner, but more woeful defending gifted the Turkish side all three points.
Icardi's penalty was poor and gave Old Trafford a lift, but a simple forward header from defender Sanchez, in his own half, evaded everyone in red and the Argentine forward raced clear to score his first Champions League goal since 2019.
The final whistle was greeted by wild scenes of celebration at Galatasaray's first Champions League away win in a decade.
The United supporters left the ground wondering when their suffering will end, having seen their side lose six of their 10 matches in all competitions this season after conceding a total of 18 goals - the most at this stage since 1966-67.