Sánchez/Ustero enter as the more structured pair: Sánchez’s left-side control and Ustero’s athletic finishing should impose longer, higher-percentage rallies. Castelló/Rufo have the firepower to create runs—especially if they speed up in Buenos Aires conditions—but they must win the mid-court exchanges to avoid being pinned in defense. Prediction: Sánchez/Ustero in 2 tight sets, with a potential tie-break if Castelló/Rufo start fast.