With Arda Güler settled on the right, Jude Bellingham free to operate inside and Kylian Mbappé leading the line, only one attacking place is left for Sunday, and OKDiario sees it as a straight contest between Diomande and Vinícius Júnior.
Diomande, 19, joined from RB Leipzig on 6 August on a contract to 2033, in a deal reported as the most expensive in Real Madrid's history. OKDiario says he was unhappy with his limited minutes early on, but Mourinho eased him in gradually, and he has now started against both Rayo Vallecano and Elche.
Against Elche he set up Mbappé and completed seven dribbles, although a mistake of his did contribute to the visitors' equaliser in a match Madrid won 3-2.
The report argues that his profile suits the Metropolitano. He has the power to cover ground, the ability to beat a man one-on-one and a willingness to help his full-back, all useful in a game where Madrid will need pace to exploit space and discipline to hold the flanks against opponents expected to make it physical. Mourinho is said to value his work without the ball.
Güler, meanwhile, is not part of the debate. He changed the game against Rayo from the bench, then scored a free-kick at Elche and completed every pass of the first half. Mourinho regards him as his conductor, and OKDiario says the coach cannot contemplate leaving him out of a fixture of this size.
That leaves Vinícius, and for the first time there is a genuine question over his place. According to OKDiario, he has lost precision and is still searching for the goal he needs, and against Elche he completed no dribbles and wasted several chances. It adds that he has also been whistled at the Bernabéu in recent games, and that Mourinho backs him in public while demanding more in private.
Dropping him would carry huge weight given his experience and his record against Atlético, but Mourinho is a believer in meritocracy and Diomande arrives in better shape.
Real Madrid go into the derby second in LaLiga on 15 points, their only defeat so far a 1-0 loss at Real Betis. Sunday's team sheet will show whether meritocracy outweighs history.