Serena Williams withdrew from her opening match at the Hopman Cup on Monday because of inflammation in her left knee, an early setback in her preparations for an Australian Open title defense.
Williams practiced ahead of her scheduled season-opener against Elina Svitolinain the international mixed-team competition at Perth Arena, but withdrew from the match and was replaced by Vicky Duval.
Duval lost 6-4, 6-1 to Svitolina and Alexandr Dolgopolov beat Jack Sock 6-4, 6-2 to clinch the best-of-three Group A match for Ukraine before the US pair won the mixed doubles 6-2, 6-3.
Williams said she expected to be able to join Sock in the US team to play the Australia Gold team on Tuesday.
Hopman Cup tournament director Paul Kilderry said Williams reported feeling pain in her knee on Sunday.
Andy Murray had a 6-2, 6-2 win over Kenny De Schepper to give Britain a 1-0 lead over France in the night match.
Dimitrov beats Simon
Brisbane: At the Brisbane International, 2015 finalist Grigor Dimitrov needed six match points before beating fifth-seeded Gilles Simon 6-3, 7-6 (10) to move into the second round.
Two-time Australian Open champion Victoria Azarenka returned from a layoff with foot and leg injuries with a 6-2, 6-0 win over Russian qualifier Elena Vesnina in her first competitive match since September.
In other matches, No. 6-seeded Carla Suarez Navarro advanced to a second-round match with local favorite Sam Stosur, who beat Slovakian Jana Cepelova 6-4, 3-6, 6-4.
Djoker wins
DOHA: Novak Djokovic opened his season with a 6-2, 6-2 win over qualifier Dustin Brown on Monday at the Qatar Open.
The top-ranked Serb avoided the post-season exhibitions last month after an exhausting 2015 season in which he won three major titles and reached the final in the other.
The Qatar Open was the only tournament in 16 played in 2015 in which Djokovic failed to reach the final, instead losing in the quarterfinals.
last year, Djokovic won a career-best 11 titles and finished with an 82-6 record.