Manchester United goalkeeper Andre Onana says it took him six months “to feel good” at Old Trafford.

United paid £47.2m to sign Onana from Inter Milan in July as replacement for four-time club player of the year David de Gea.

However, despite lofty expectations on his arrival, the Cameroon international was chipped from 50 yards on his Old Trafford debut against Lens and then made a series of errors that contributed to the club’s poor Premier League form and Champions League group-stage elimination.

Onana’s performances didn’t improve significantly until after he returned from the Africa Cup of Nations in February and while he has made the odd mistake, he is now regarded as one of the more reliable members of manager Erik ten Hag’s squad as they head into Saturday’s FA Cup final against rivals Manchester City (15:00 BST).

“I arrived as the best goalkeeper in the world and ‘boom’ it went down. It was like ‘what happened?’,” said the 28-year-old.

“But that is how difficult football is sometimes. It depends if you want to stay down there or stand up and fight. I know what I did to arrive here. I know who I am. I decided to stand up and fight.”

Onana cites the example of team-mate Marcus Rashford for why players need to avoid the extremes of judgement.

Rashford scored a career-high 30 goals last season. This term, he has managed eight and didn’t even make England boss Gareth Southgate’s provisional 33-man European Championship squad, let alone the final cut.

“We are talking about the same player,” said Onana. “So now he’s a bad player? No. You can have a bad season or a bad start but the most important thing is how you end.

“Rashy, for me, is one of the best players in the world. But he is facing difficulty. It’s not only him and me but the whole club.

“But he will come back. I know my killer will score some important goals for us. Hopefully against City he will score two and we win the FA Cup.”

The wariness among some United fans about a second consecutive FA Cup final showdown with Manchester City comes from the sheer number of chances their side allows.

There was a seven-game streak between March and April where the opposition had a minimum of 20 shots per match on Onana’s goal.

When they last played City in March, they had three shots to their opponents’ 27 in a 3-1 defeat.

Onana feels this is purely as a consequence of the changes Ten Hag has had to make to his defence.

The partnership between Casemiro and Lisandro Martinez that started at Brighton on 19 May was the 15th different central defensive combination United have deployed this term. No partnership has started more than four consecutive games.

“I don’t mind facing 20 or 30 shots,” said Onana. “I am very happy with what my team-mates are doing because a lot of them make sacrifices for the team.

“It would be nice to have everyone back but what can we do? Hide? We are a big club. We have to go on the front foot and deal with difficulties. I am positive. I know things will get better. If not today, tomorrow.”

Onana does not take too much notice of the overwhelming odds in favour of City repeating their triumph of 12 months ago, when United conceded after 12 seconds, the fastest goal in FA Cup final history.

He was part of the Inter Milan side who made life exceptionally difficult for City in last season’s Champions League final and were the better team in periods before eventually losing to Rodri’s decisive strike.

Saturday is clearly a game of huge significance for Ten Hag, whose United future remains open to question.

Onana knows the Dutchman well, having worked with him at Ajax for five years before both left in the same summer, with Ten Hag joining United as he left for Italy.

“I’m not here to back him because he’s big enough to back himself,” said Onana. “But he’s a really good guy, a positive coach and tactically he is good.

“If he had all his squad together, it would probably be different for him, for us, the club and the fans.

“We know how good City are. They are the best team at the moment and we lost twice to them already.

“But we are motivated. Beating them wouldn’t make it a successful season. Playing for this club, I don’t think winning the FA Cup is enough.

“But it would make things look better. We go there to win.”