No one saw what was coming next. Real Madrid suddenly entered the picture.
The Athletic revealed in late June that new coach José Mourinho, back at Real Madrid 13 years after his first spell ended, was monitoring a right winger alongside the club's scouting team.
Real Madrid were trying to offload Brahim Díaz at the same time, despite the player wanting to stay. Rumours swirled about the club's interest in Bayern Munich's Michael Olise, yet Real Madrid denied it in private and even issued an official statement rejecting the existence of any negotiations.
Reports kept linking Olise to the club, but behind the scenes the management were working on the Diomande deal. Mourinho and the Real Madrid hierarchy sat down in planning meetings and agreed the right side of the attack needed strengthening.
They had noticed the team leaned heavily on the left flank, where Vinícius Júnior shines and both Jude Bellingham and Kylian Mbappé make a significant impact.
The feeling inside Real Madrid was that the lack of attacking threat on the opposite flank was limiting their options and making life easier for opposing defenders. Mourinho, who played a pivotal role in the negotiations, laid out this vision to Diomande directly.
Nathan Campbell, head of global player recruitment at ROC Nation and Diomande's agent, said: "The final piece that sealed everything was José Mourinho."
He added: "He spoke to him in fluent French, and that had a huge impact on him. We did not know that Mourinho spoke French so fluently, because he had never coached any French club. But the timing of the call he made with Yan, and the way he spoke to him in fluent French about his ideas, the project, and how he would fit into the team, showed that he was placing great importance on this conversation. That was a decisive point, and it was the key to convincing him."
Real Madrid also reached for one of their usual touches in deals like this, presenting Diomande with a white shirt bearing the club crest.
It went further still. They handed him a clear plan for his career, mapping out his individual and collective development at the club. It even included case studies, among them how Vinícius Júnior's career had grown since he joined the Bernabéu.
Michael Yormark, international president of ROC Nation, said the hard work and sacrifices Diomande has made throughout his career are the reason he is "achieving his dream" of playing for Real Madrid.