(Reuters) – Serena Williams and Ekaterina Makarova sprinted into the semi-finals of the U.S. Open on Wednesday but marathon man Kei Nishikori had to go the distance to upset Stan Wawrinka and become the first Japanese man into the last four of a grand slam in 81 years. On a sultry evening, Williams sleepwalked through the start of her quarter-final with Flavia Pennetta as the 12th seeded Italian broke twice on the way to a […]