Johannesburg – A first-round defeat at the Atlanta Open caused South Africa's top men's tennis player Kevin Anderson to slip out of the top 20 in the latest ATP World Tour singles ranking on Monday.

Anderson dropped from a career-high 17th place to 21st following his 6-4 7-5 defeat by 142nd ranked Dutchman Thiemo de Bakker on Friday.

It was Anderson's first game since he was beaten by Andy Murray in the last-16 round at Wimbledon almost four weeks ago, which earned him his career highest ranking.

Meanwhile, Ruan Roelofse shot up 126 places from his previous ranking of 736 to 610 in the latest ratings.

South Africa's number one female tennis player, Chanelle Scheepers, remained 71st in the world rankings. – Sapa