Stan Wawrinka in semi-finals

Switzerland’s third-seeded Wawrinka, playing his first tournament in the United States since his US Open victory last year, battled for two and a half hours to get past the rising Austrian star 6-4, 4-6, 7-6 (7/2) and book a meeting with Spain’s Pablo Carreno Busta. Carreno Busta saved two match points en route to a 6-1, 3-6, 7-6 (7/4) victory over Uruguay’s Pablo Cuevas. Later, Elena Vesnina beat Venus Williams 6-2 4-6 6-3 while Mladenovic, the 28th seed, continued an impressive run of form beating 13th seed and 2011 winner Wozniacki 3-6 7-6(4) 6-2 to reach her first Premier Mandatory semi-final and guarantee her debut in the Top 20.