Novak Djokovic defeated Feliciano Lopez 6-1, 3-6, 6-3, 7-6 to reach the US Open Men's Singles semi-finals, a 21st last-four spot in his last 22 Grand Slams. The top seed and 2011 champion, playing in his 26th consecutive quarter-final at the majors, claimed his 55th match win in New York. Marin Cilic reached the semi-finals with a 6-4, 6-4, 3-6, 6-7, 6-4 win over France's Jo-Wilfried Tsonga.In Women's Singles, World number one Serena Williams stayed on course for the first calendar Grand Slam since 1988, advancing to the US Open semi-finals Tuesday by defeating older sister Venus Williams 6-2, 1-6, 6-3.Three-time defending champion Serena reached a Thursday semi-final against Italy's 43rd-ranked Roberta Vinci, who eliminated France's 40th-ranked Kristina Mladenovic 6-3, 5-7, 6-4.