Serena Williams has warned her opponents at this week’s WTA season-ending championships in Istanbul that she can still improve.
Williams has been on a remarkable run since winning Wimbledon last year, collecting 15 singles titles – including four grand slams and an Olympic gold medal – and losing only five matches.
“It’s definitely one of the best years I have had,” the world No 1 said. and I’m still looking to improve. I’m so excited for next year when I can take my game to a new level.”