Ustero/Sánchez enter as the more established, higher-tempo pair: Sánchez’s control and net management should steady Ustero’s explosiveness in Brussels’ typically heavier indoor conditions. Goenaga/Caldera can compete if they win first-volleys and target transitions, but they’ll need sustained serving accuracy to avoid being pinned in defense. Prediction: Ustero/Sánchez in 2, with a tighter second set if Goenaga/Caldera dominate the middle early.