BUENOS AIRES - Top seed and defending champion Rafael Nadal reached the Argentina Open semi-finals Friday, braving sweltering temperatures of 33 degrees to clinch a 7-6 (7/3), 6-2 win over Italian journeyman Paolo Lorenzi. Nadal, the world number five, is back on his favourite clay court surface and is playing his first event since his shock opening round loss to compatriot Fernando Verdasco at the Australian Open last month. He had seen off close friend Juan Monaco of Argentina in Thursday's first round but faced a slightly tougher test Friday when 34-year-old Lorenzi, the world 52, clawed his way back from a 4-1 first set deficit. But 29-year-old Nadal clinched victory on his first match point after one hour and 51 minutes on court. It was the Spaniard's 346th win on clay.