Sainz/Eugenio come in as the more stable pair for a P2: Sainz typically anchors the left with heavier volume and better net management, while Eugenio can finish when they gain court position. Casali/Domínguez need to disrupt rhythm with speed and first-volley pressure, because in longer, structured rallies Sainz’s control usually tilts the balance. In Gijón’s likely cooler indoor conditions, I’d edge Sainz/Eugenio in two tight sets if they hold the net.