The Ivorian winger's arrival, in a package reportedly worth between €115m and €120m from RB Leipzig, represents a significant shake-up of Madrid's attack, with Vinícius the player most directly affected.
The Brazilian is holding firm on a request for a loyalty bonus of the kind Neymar and Lionel Messi once secured at Barcelona, a precedent Real Madrid have never entertained and have no intention of setting now, wary of other players making similar demands if they did, reports OKDiario.
That sticking point is the main obstacle to Vinícius extending his stay, and the club has not simply waited for him to soften his stance: sporting sources indicate personal terms remain far apart even as talks continue, with the Brazilian's current deal running until 30 June 2027 and Arsenal reported to have made preliminary contact over a possible move, whether he leaves this summer or lets his contract run down.
Diomande, comfortable on either flank and renowned for his explosive pace and dribbling, gives José Mourinho a ready-made alternative regardless of how the Vinícius situation resolves itself. The 19-year-old scored 12 goals and provided eight assists in the Bundesliga last season, form that earned him the division's Best Newcomer award, and Real Madrid's willingness to commit such a fee to his signing underlines their determination to plan for the future even as Vinícius's situation remains unresolved.
Paris Saint-Germain had also pursued Diomande earlier in the process before pulling out, citing the scale of the financial demands from the player's camp as a threat to the balance of their squad.
Should Vinícius ultimately run down his contract, he would face considerably more time on the bench than he would like, with Real Madrid increasingly building around the younger winger as a cornerstone of their long-term plans.
For now, the club insists no scenario is being ruled out, but having already secured a ready alternative, the balance of leverage in the Vinícius negotiations appears to have shifted decisively in Real Madrid's favour.