Serena Williams has withdrawn from this month’s season-ending WTA Finals in Singapore citing a persistent shoulder injury, said the world number two on Monday. The 22-time grand slam singles champion has played only eight tournaments this year and lost her spot at the top of the world rankings to German Angelique Kerber last month. “It’s been a really tough year for me, dealing with these shoulder injuries,” said the 35-year-old. “My doctor insists that I stay home and heal it. I only have wonderful memories of playing in Singapore and I will really miss my fans.” BREAKING: @SerenaWilliams has withdrawn from #WTAFinals . This is her message to the fans. Get well soon Serena! pic.twitter.com/E9GfwjERc0 — WTA (@WTA) October 17, 2016 <!--//--><![CDATA[// ><!--\n\n\n//--><!]]> Williams pulled out of two tournaments in China after being knocked out in the semi-finals of the US Open. That defeat saw Williams’ 186-week reign at the top of the world rankings end as Kerber reached the summit after capturing the title at Flushing Meadows. Williams claimed just one grand slam title in 2016 at Wimbledon before shoulder troubles hampered her in Rio de Janeiro where her hopes of a fifth Olympic Games gold medal were ended in the third round.