Manchester United's woeful season lurched from one damaging loss to another as Galatasaray took advantage of some calamitous defending to record a comeback Champions League win at Old Trafford.
Ten-man United led twice through young striker Rasmus Hojlund, the second a brilliant effort as the 20-year-old took advantage of Davinson Sanchez's slip to race 50 yards and beat Fernando Muslera with a deft finish.
But the hosts could only hold their advantage for a combined 10 minutes, as first old-boy Wilfried Zaha, then Kerem Akturkoglu levelled.
Then, after Mauro Icardi had failed to convert the penalty that followed a terrible Andre Onana mistake that led to Casemiro's red card, the Argentine made amends when he sped clear of the hosts' defence nine minutes from time and found the finish.
It is the first time United have started a Champions League group-stage campaign with successive defeats, and piles the pressure on manager Erik ten Hag, whose side are bottom of the table, four points behind their visitors who are second, behind Bayern Munich.
United have now lost two on the trot following Saturday's Premier League defeat by Crystal Palace, five of their past seven games and six out of 10 in all competitions since the start of the season.
Terrible night for Ten Hag
This was a truly awful night for Ten Hag, who stood in the pouring rain before the final whistle hoping his side could snatch something to give them hope in a campaign that has been as bleak as the weather.
"Our start to the season has not been good enough," he said in his programme notes. "Although there are reasons, we will not attempt to hide behind excuses. It is up to us to now to turn our fortunes around. What happens next is up to us and nobody else."
The early signs are not good.
Hojlund at least provides something positive to reflect on for United.
Marcus Rashford created the Dane's first with a lofted cross into the six-yard box, where Hojlund beat Sanchez to thump home a header.
Then, after Rashford had sprinted clear only to mess up a routine square pass that should have presented Bruno Fernandes with a tap-in, Hojlund embarked on his own run from halfway, this time with considerably more success to take his Champions League tally to three in two games.
Defensively though, United were shocking from that point on.
Casemiro failed to track Akturkoglu's run into the box after Sofyan Amrabat had been turned too easily by the touchline, and the Turkey international levelled for a second time.
Onana's £47m price-tag came with the assurance he is good with his feet. But when the Cameroon keeper sent a pass from the edge of his six-yard box straight to Dries Mertens, his goal only survived because Casemiro fouled the Belgian and Icardi missed the penalty.
There was no reprieve when Icardi won it four minutes later, and the jubilant celebrations of visiting fans scattered all over Old Trafford only made a bad night worse for United.
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Squad number24Player nameOnana
Squad number20Player nameDiogo Dalot
Squad number19Player nameVarane
Squad number2Player nameLindelöf
Squad number4Player nameS Amrabat
Squad number46Player nameMejbri
Squad number18Player nameCasemiro
Squad number7Player nameMount
Squad number8Player nameBruno Fernandes
Squad number11Player nameHøjlund
Squad number10Player nameRashford
Squad number9Player nameMartial
Squad number14Player nameEriksen
Squad number17Player nameGarnacho
Squad number21Player nameAntony
Squad number1Player nameMuslera
Squad number93Player nameBoey
Squad number6Player nameD Sánchez
Squad number42Player nameBardakci
Squad number3Player nameAngelino
Squad number23Player nameAyhan
Squad number34Player nameTorreira
Squad number20Player nameTetê
Squad number7Player nameAktürkoglu
Squad number14Player nameZaha
Squad number9Player nameIcardi
Squad number10Player nameMertens
Squad number25Player nameNelsson
Squad number27Player nameSérgio Oliveira
Squad number53Player nameYilmaz
Squad number91Player nameNdombélé
Formation 4-3-324Onana20DalotBooked at 38mins19Varane2Lindelöf4S AmrabatSubstituted forMartialat 89'minutes46MejbriSubstituted forEriksenat 45'minutes18CasemiroBooked at 77mins7MountSubstituted forAntonyat 85'minutes8Bruno Fernandes11Højlund10RashfordSubstituted forGarnachoat 68'minutes
Formation 4-2-3-11Muslera93BoeyBooked at 61mins6D Sánchez42Bardakci3AngelinoSubstituted forNdombéléat 84'minutes23AyhanSubstituted forNelssonat 84'minutes34TorreiraBooked at 31minsSubstituted forOliveiraat 61'minutesBooked at 85mins20TetêSubstituted forYilmazat 61'minutes7Aktürkoglu14ZahaSubstituted forMertensat 72'minutes9Icardi
Match ends, Manchester United 2, Galatasaray 3.
Second Half ends, Manchester United 2, Galatasaray 3.
Hand ball by Diogo Dalot (Manchester United).
Rasmus Højlund (Manchester United) wins a free kick on the left wing.
Foul by Victor Nelsson (Galatasaray).
Offside, Manchester United. Christian Eriksen tries a through ball, but Anthony Martial is caught offside.
Attempt missed. Mauro Icardi (Galatasaray) right footed shot from the centre of the box is close, but misses to the right. Assisted by Sacha Boey with a cross.
Attempt blocked. Bruno Fernandes (Manchester United) right footed shot from outside the box is blocked.
Bruno Fernandes (Manchester United) wins a free kick in the attacking half.
Foul by Sérgio Oliveira (Galatasaray).
Substitution, Manchester United. Anthony Martial replaces Sofyan Amrabat.
Delay over. They are ready to continue.
Delay in match because of an injury Davinson Sánchez (Galatasaray).
Attempt missed. Sérgio Oliveira (Galatasaray) right footed shot from long range on the right is too high. Assisted by Dries Mertens.
Sérgio Oliveira (Galatasaray) is shown the yellow card.
Foul by Rasmus Højlund (Manchester United).
Sérgio Oliveira (Galatasaray) wins a free kick in the defensive half.
Substitution, Manchester United. Antony replaces Mason Mount.
Attempt missed. Victor Nelsson (Galatasaray) header from the centre of the box is close, but misses to the left. Assisted by Sérgio Oliveira with a cross following a corner.
Substitution, Galatasaray. Victor Nelsson replaces Kaan Ayhan.
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