Novak Djokovic defeated Feliciano Lopez 6-1, 3-6, 6-3, 7-6 (7/2) to reach the US Open semi-finals, a 21st last-four spot in his last 22 Grand Slams.Top seed and 2011 champion Djokovic will face defending champion Marin Cilic in Friday`s semi-finals.Cilic reached the semi-finals with a 6-4, 6-4, 3-6, 6-7 (3/7), 6-4 win over France`s Jo-Wilfried Tsonga.