Japan's Kei Nishikori geastures to the crowd after winning against Switzerland's Stan Wawrinka during their round robin stage men's singles match on day two of the ATP World Tour Finals tennis tournament in London. Pic/AFP

London: Japanese tennis player Kei Nishikori successfully started the ATP World Tour Finals with a victory over Swiss Stan Wawrinka 6-2, 6-3 in the John McEnroe Group.