Rafa Nadal was knocked out of the Madrid Open quarter-finals stage 6-4 6-4 by German Alex Zverev on Friday. Nadal, a five-time winner in the Spanish capital, was the favourite and top seed having lifted the Barcelona Open trophy last month but played below par on a sweltering spring day. Zverev struggled in the opening exchanges, finding himself 4-2 down before breaking Nadal twice to turn the match on its head and take the first set. The fifth-seeded German then powered ahead in the second, breaking Nadal"s serve again and holding out to seal a career-first win on clay against the Spaniard. He will take on third seed Dominic Thiem in Saturday"s semi-final after the Austrian overcame John Isner 3-6 6-3 6-4. Later on Friday, Alexander Bublik of Kazakhstan plays fellow qualifier Casper Ruud from Norway while eighth seed Matteo Berrettini of Italy faces Chilean 16th seed Cristian Garin.