Serena Williams crashed out of the US Open Tennis Tournament. Her semi-final defeat to Karolina Pliskova costing her a shot at a 23rd grand slam title and a record 187th straight week at number one. Pliskova, the 10th-seeded Czech playing in her first grand slam semi-final, triumphed 6-2, 7-6 and will face either Caroline Wozniacki or Angelique Kerber, who will supplant Williams atop the summit when the new world rankings are released