Serena Williams stunned by Karolina Pliskova in 2016 US Open semi-final

Serena Williams stunned by Karolina Pliskova in 2016 US Open semi-final Serena Williams stunned by Karolina Pliskova in 2016 US Open semi-final -Serena Williams' 186-week reign as world No.1 is over after Karolina Pliskova beat her 6-2 7-6 (7-5) in the semi-finals of the US Open. The 10th-seeded Czech moves into the final at Flushing Meadows to meet either Angelique Kerber - who will replace Williams as the world's top-ranker player - or Caroline Wozniacki.