Johannesburg - South Africa's Kevin Anderson retained his career-high 18th placing when the latest ATP World Tour singles rankings were released on Monday.
The 27-year-old's position remained unchanged despite beating world number three and Switzerland's number one Stanislas Wawrinka in the fourth round of the BNP Paribas Open last week.
Anderson had already beaten veteran Australian Lleyton Hewitt in the second round, before upsetting Wawrinka 7-6, 4-6, 6-1, to set up a quarterfinal meeting with Roger Federer.
Federer eased past the South African in straight sets.
Anderson was also runner-up in the previous week's Mexican Open in Acapulco.
South Africa's top-ranked women's player, Chanelle Scheepers, dropped four spots to 78 in the latest women's world tennis rankings, while doubles player Raven Klaasen remained at 30 for a second consecutive week.
Lucas Sithole held onto the second spot in the men's singles quads division for yet another week, a position he had held since early September.
He also remained eighth in the quads doubles rankings.