Manchester United endured more misery as they slumped to a 3-2 defeat to Galatasaray at Old Trafford on Tuesday to leave them bottom of Champions League Group A.
United were hoping to recover from a fourth Premier League defeat of the season against Crystal Palace on Saturday and made a good start in the Manchester rain on Tuesday, racing into a 17th-minute lead through Denmark striker Rasmus Hojlund.
Their advantage lasted less than six minutes as Wilfried Zaha, playing against his former club, scooped home the equaliser after poor defending from the hosts, which has become a regular feature.
After the break, Hojlund capitalised on a mistake from Galatasaray defender Davinson Sanchez to put United back in front in the 67th minute. However, Kerem Akturkoglu drew level four minutes later to stun Old Trafford into silence.
A mistake from United goalkeeper Andre Onana forced Brazilian midfielder Casemiro to concede a penalty, which saw him sent off after receiving a second yellow card.
Mauro 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 and rock bottom.
It was United's sixth defeat in 10 games this season and the Red Devils are in danger of an early exit from the Champions League.
Meanwhile, Arsenal slumped to a first defeat of the season as Lens came from behind to win 2-1 in France thanks to a fine second-half strike by Elye Wahi.
Gabriel Jesus gave the Premier League side an ideal start when he opened the scoring in the 14th minute. But Adrien Thomasson soon brought last season's Ligue 1 runners-up on level terms while the visitors saw Bukayo Saka limp off before half-time.
Wahi then fired home in the 69th minute and his side held on for a famous victory.
Also, Real Sociedad picked up their first win in the group stage of the Champions League in two decades with a 2-0 win at Salzburg.
Mikel Oyarzabal and Brais Mendez scored first-half goals for Sociedad, who took the Group D lead. The Spanish club have four points after two matches, while Salzburg stay on three points. Inter Milan joined Sociedad at the top by beating Benfica 1-0.
In another match, Thomas Muller came off the bench to set up the winning goal for fellow substitute Mathys Tel as Bayern Munich came from a goal down to beat Denmark's FC Copenhagen 2-1.
The 34-year-old Muller entered the game in the 77th minute and used his experience to first outrun the defence and then out-muscle it before teeing up Tel to take all three points.
Bayern did not manage a shot on target until late in the first half as Copenhagen's compact defence stood tall.
That allowed the home side to take a shock lead in the 56th minute when Bayern failed to clear Viktor Claesson's shot, and midfielder Lukas Lerager followed up with a clever drive to put the Danish champions in the driving seat.
Bayern struck back in the 67th minute as Jamal Musiala dispatched a low shot into the corner of the net beyond the dive of Kamil Grabara.
Substitute Muller wasted no time getting involved as he crossed for Leon Goretzka, but the midfielder's header drifted wide of the target. Undeterred, Muller embarked on a lung-busting run to track down Harry Kane's flick-on, and he firmly stood his ground before passing for Tel to fire home the winner two minutes later.