Serena Williams rarely backs down in a scrap but she was spared a fight for the honour of ending the year as world number one yesterday when her rival Dinara Safina quit the WTA Championships with injury.

Sports minister Gerry Sutcliffe has warned top footballers that they need to act as role models and said there should be a debate about whether to impose points deductions for clubs whose players are guilty of serious misbehaviour.

There were some who thought Serena Williams should have been banned from the rest of the tournament after her expletive-filled outburst at a line judge here on Saturday, but the American was back on court in Arthur Ashe Stadium yesterday.

There was about as much chance of Serena Williams following Dinara Safina and Maria Sharapova out of the US Open here yesterday as there was of the American conceding that she should not be regarded as the world's best player. Daniela Hantuchova has reached one Grand Slam semi-final and three quarter-finals, but the 26-year-old Slovak offered minimal resistance as Williams powered into the quarter-finals with a 6-2, 6-0 win in just 64 minutes.

America was able to celebrate two successes here on this Independence Day holiday weekend, thanks to the Williams sisters winning Saturday's ladies doubles after Serena had lifted the solo crown, but the US endured disappointment in other finals. The Californian twins, Bob and Mike Bryan, ranked No 1 in the men's doubles, lost Saturday's final in that event to Daniel Nestor of Canada and Nenad Zimonjic of Serbia.

Serena Williams turned the tables on sister Venus to win her third Wimbledon title with a 7-6 (7/3) 6-2 victory on Centre Court.