ISTANBUL -- "Your nightmare is back again" read one of the banners at Galatasaray's Rams Park. For André Onana, who is making a habit of Champions League howlers, it was especially true.

After errors against Bayern Munich away and Galatasaray at home already this season, the Cameroon goalkeeper made two catastrophic mistakes to gift the Turkish champions a 3-3 draw in Istanbul on Wednesday and leave Manchester United's Champions League hopes hanging by a thread.

Erik ten Hag's team twice had the game won at 2-0 and 3-1 up, but with one round of fixtures left, they are anchored to the bottom of Group A. Only a team as frail as this United one could score nine goals in three European away games and fail to win any of them.

In their five Champions League games this season, they've conceded 14 goals. Only Royal Antwerp, who have lost every game in the group stage, have conceded more.

- Stream on ESPN+: LaLiga, Bundesliga, more (U.S.)

"We win and lose together," Ten Hag said after the match, refusing to blame Onana, his 43 million summer signing from Inter Milan. "You see the progress in this team. I take many positives from this game. Some mistakes, we played like I want my team to play. It was enjoyable to watch that: proactive, dynamic, brave and we scored great goals. Even after we had some setbacks, we kept going until the end and we should have won with big chances from Scott McTominay and Facundo Pellistri.

"Of course, I am disappointed because we should have managed the game better, we will learn from that."

The biggest frustration for Ten Hag will be that before Onana's mistakes, his players had done the hard bit and, for large spells, were by far the better team. The teams walked out onto a sodden pitch after torrential rain in the Turkish capital for more than 24 hours and were greeted with a huge banner that read "Welcome to hell," but United had quietened the fiery atmosphere in the stadium inside the first 20 minutes.

First it was Alejandro Garnacho who, after an overhead kick for the ages against Everton on Sunday, had the confidence to walk into hell and tell everyone to calm down. After a flowing team move, the 19-year-old smashed his finish into the roof of the net and then rubbed it in with a "calma, calma" celebration in front of the Galatasaray fans, who responded with a volley of missiles thrown from the stands.

Captain Bruno Fernandes was left to pick up the objects and remove them from the pitch before coming up with a missile of his own.

Picking up the ball from Luke Shaw on the left, he took a couple of strides forward and launched a rocket into the top corner with his right foot from 25 yards. His celebration was to slide on his knees and cover his ears, but he needn't have bothered as the ear-splitting noise was replaced with stunned silence.

Ten Hag spoke afterward about his team being better at "game management," but that felt like it ignored the fact that without Onana's contribution, they would have almost certainly won as Hakim Ziyech was twice the beneficiary of free-kick goals that should have been saved.

The first wrong-footed Onana as it slid past his right knee, but his mistake for the second -- after McTominay had scored United's third -- was the kind that ends up on DVDs of football's biggest blunders. He perhaps thought Anthony Martial would head Ziyech's cross clear, but without a touch from the French forward, the United No. 1 ended up being surprised by the pace of the ball and punching it into his own net.

He could do little to stop substitute Kerem Aktürkoglu's bullet finish to make it 3-3. By that stage, though, the damage had already been done.

At the final whistle, Onana stood crestfallen on the pitch and had to be consoled by his backup Altay Bayindir, Galatasaray goalkeeper Fernando Muslera and Ziyech, as his United teammates trudged off down the tunnel.

"He is OK," Ten Hag said of Onana. "As I said, it is not about individuals. Of course, individual errors in football can make a difference and you take responsibility for it, but it is always about the team. This team is good, all the players in the squad are good and deserve the best, to play for Manchester United, because they are brilliant players. And that counts for the whole squad.

"As a team, we have to learn because we are conceding too many goals and it is unnecessary and avoidable. I am sure our team is experienced enough and capable enough to manage this, and we will do better."

Vulnerability at the back has become the story of the group stage campaign, but regardless of whether Ten Hag wants to admit it, Onana has contributed more than most with big mistakes in pivotal moments. The latest episode of his recurring nightmare has left United facing Champions League oblivion.