Man United goalkeeper Andre Onana had to protect his mental health after poor start at the club

In his own words, Andre Onana arrived at Manchester United last year as the "best goalkeeper in the world."

Within weeks his reputation had taken a battering and he was left needing to protect his mental health.

"It was for me in certain moments like 'What happened?'" Onana said as he prepared for Saturday's FA Cup final against Premier League champion Manchester City at Wembley Stadium.

A serial title winner with Ajax and a Cameroon international, Onana moved to United from Inter Milan for $57 million in the offseason. As a modern ball-playing keeper, he was seen as pivotal to manager Erik ten Hag's plans to mount a Premier League and Champions League challenge.

But a series of costly errors in his opening weeks at the club saw him become a figure of ridicule on social media and a symbol of United's troubled campaign.

"When I arrived here, I arrived as the best goalkeeper in the world and 'boom' it went down and you see how difficult football is sometimes," Onana said. "I decided to not stay there, but to stand up and fight to the end. I know who I am. I know what I did to arrive here and never forget what you did.

"Never stay too high, but also don't stay too low because at the end of the day, being a player for such a big club, when you win it's top and when you don't win it's terrible. You have to stay in between and feel your mind and have your mental health safe because it is not easy to play for such a big club."

The 28-year-old Onana said it took him six months to "feel good" at United. For all his difficulties, he was brave enough to accept culpability and give interviews after an error-strewn performance in a loss to Bayern Munich in the Champions League in September. But the blunders kept on coming.

Eventually Onana's form improved. United's didn't.

Saturday represents the last chance to salvage a season that has seen the 20-time league champion suffer its lowest finish in the Premier League era — eighth. There were 14 league defeats — the most in 34 years.

Victory against City, which has replaced United as the dominant force in English football and is looking to become the first team to win back-to-back league and FA Cup doubles, would at least end the season on a high. It would also secure United a place in the Europa League.

Onana accepts even a win wouldn't represent a successful campaign.

"Playing for this club, winning the FA Cup I don't think it's enough. We're used to playing in the Champions League, some of us have played in Champions League finals. It's been a difficult season," he said.

Saturday's game is a rematch of last year's final, which City won 2-1 on the way to a treble of trophies including the Premier League and Champions League.

Onana wasn't involved in that match because he hadn't yet completed his move to Old Trafford. But the game represents a rematch for him on a personal level after his Inter Milan team lost 1-0 to City in last year's Champions League final.

He was outstanding in the match in Istanbul, but still came up short. He said that game can be an inspiration for United because Inter was also an underdog, but came close to producing an upset.

"If you face City already thinking they are going to win then don't step on the pitch," he said. "They are the best team in the world at the moment. Last year in the Champions League final we (Inter) were better than them. They were lucky to win against us."

Even a win might not be enough to save Ten Hag's job. His position is unclear amid mounting speculation about his future and the overhaul being carried out by United's new co-owner Jim Ratcliffe.

Onana was part of Ten Hag's three-time Dutch title-winning team at Ajax and has no doubt about his abilities.

"We cannot hide. We are such a big club. We have to go front foot and deal with the difficulties and hopefully things will change. I know they will change, if not today, then tomorrow," he said.