Serena Williams hits rankings milestone

Serena Williams is firmly on course to achieve at least the second-longest streak at the top of the WTA rankings, after completing a 150th successive week as world number one.

Williams regained pole position in the rankings in February 2013 and has remained at the summit ever since.

The 34-year-old American, who claimed three grand slams this year to take her overall tally to 21, is now just six weeks shy of Martina Navratilova's 156-week stint at number one from June 1982 to June 1985.

Steffi Graf's record of 186 straight weeks as the top-ranked women's singles player also appears well within Williams' reach given her domination of the WTA Tour this year.

Williams lost only three of her 56 tour matches in 2015, a shock US Open semi-final loss at the hands of Roberta Vinci derailing her bid for a first calendar-year Grand Slam.