Former world No 1 tennis player Venus Williams has been forced to pull out of this month's season-opening Brisbane International tennis tournament.

The 39-year-old, seven time grand slam champion suffered an "unexpected setback" in training but still hopes to compete in the Australian Open at the end of the month.

Williams has not won a grand slam since she claimed her fifth Wimbledon title in 2008 and has since suffered numerous injuries as well as suffering from Sjögren's syndrome. This is an auto-immune disease with a wide range of symptoms ranging from joint pain and dry mouth to swelling, numbness, digestive problems and fatigue. 

A replacement for the World No 52 has not yet been announced but other high profile players including world No 1 Ashleigh Barty, defending Champion Naomi Osaka, and wildcard Maria Sharapova are all preparing for the first tournament of the year.

The Brisbane International starts on January 6 ahead of the Australian open, which begins on January 20.