The Johan Cruyff Arena, 9 April 2022, and André Onana is being booed by his own Ajax fans, at his home ground, during a 2-1 win over Sparta Rotterdam as Erik ten Hag’s team move closer to the Eredivisie title. Asked about this the goalkeeper nicknamed the Cameroon Cat by supporters in warmer times offers a pithy take. “I’m not affected, I don’t care at all. They can sing, they can cry, they can do whatever they want.”

When it is put to him that their dudgeon may be related to his decision not to sign a new deal and to join Internazionale in the close season on a free, Onana is nonplussed: “You have to ask them.”

This is, though, the reason. Onana’s refusal to agree fresh terms with Ajax disappointed (to characterise it lightly) fans and the club, which felt its loyalty in supporting and continuing to pay him when he served a nine-month drug ban had not been repaid.

The summer before, had he not been suspended, Onana might have drawn a €30m to €40m fee, a relative fortune for a then debt-riven Ajax.

But, no. After Onana had his 12-month ban for ingesting Lasimac, which contains a banned Furosemide-based diuretic, reduced by the court of arbitration for sport to nine months, he was available again in November 2021. He played once, against Besiktas, before not being seen in Ajax colours again until 27 February, a 2-1 defeat at Go Ahead Eagles.

Onana’s form was fitful – he committed an error for Cameroon that allowed Burkino Faso’s opener in the Africa Cup of Nations that January – and his Ajax career ended after appearances in eight consecutive matches with his message to jeering fans.

When he did not feature in the side for the KNVB Cup final against PSV Eindhoven the following week Ten Hag cited a “groin problem”, though reports in the national press during the buildup suggested the veteran Maarten Stekelenburg was always going to be chosen. If all of this strained relations between Onana and Ten Hag, the Manchester United manager obviously no longer cares after the player’s impressive season at Inter.

But you can still wonder whether his decision to replace David de Gea with Onana will prove a masterstroke or misstep. Onana, who is due for a medical and to sign his contract, is certainly a strong character. At the Qatar World Cup in November, he was sent home by Rigobert Song for his refusal, according to reports, to heed the Cameroon head coach’s instruction to play “safer” balls to the “sides” rather than through the middle.

André Onana playing for Cameroon in the Africa Cup of Nations

André Onana plays for Cameroon but has had a stormy relationship with his international manager, Rigobert Song. Photograph: Mohamed Abd El Ghany/Reuters

There may be two red flags here. First, Onana’s apparent defiance of the man with more authority than him – an anti-team ethic and disrespectful conduct Ten Hag would never countenance. And, just as crucially, whether he is genuinely too risky when passing out from the back. Onana’s skill with the ball at his feet is a key attribute in his recruitment, De Gea’s questionable ability in this area a reason he was allowed to leave.

Setting aside the episode with Song, Onana has established a firm reputation for being an accomplished footballer who, if he does take the occasional gamble, is considered a brave, initiative-taking keeper who wishes to be the first point of attack. All of which derives from his beginnings as a 14-year-old at Barcelona.

Ten Hag will, of course, be versed in Onana’s game. Having been his boss for four and a half years at Ajax, he acquires a third footballer he has previously worked with, the 27-year-old following Lisandro Martínez and Antony. It also adds a player whose experience grew vastly in the year they were apart. Onana arrives as a Champions League finalist and although Inter lost 1-0 to Manchester City in Istanbul he decorated the showpiece with a display that wowed Uefa’s technical observers.

In their report they said: “The evolution of the goalkeeper goes on with Inter’s André Onana less a sweeper-keeper than a holding midfielder at times according to Roberto Martínez as he reflected on the Cameroonian’s impressive passing range. Goalkeepers are increasingly taking higher positions as they help make the play and Onana embodied this shift in the final – one of five matches in Inter’s campaign in which he completed 30 or more passes.

“One pass in the final summed up his impact as he drove the ball low to Lautaro Martínez in the opposition half, taking out six City players to help create a Romelu Lukaku chance.”

This last sentence could have been written about Ederson, Pep Guardiola’s keeper, whose long-range, laser-like passes have added an extra dimension to England’s pre-eminent team.

A goalkeeper cannot post a better calling card than performing as a “holding midfielder” in the continent’s biggest club game. If Uefa’s experts are correct, it suggests Ten Hag’s second summer addition will elevate his side. And, perhaps, continue the revolution Guardiola has brought to the English game via Ederson’s passing ability and prove a vital part in United’s attempt to catch and overtake City’s treble winners.