<p class="title">Serena Williams made a winning return to competitive action at the Hopman Cup on Monday but could not prevent the United States from losing 2-1 to Greece in their opening round-robin match.</p>.<p class="bodytext">Williams, playing her first competitive match since losing the US Open final to Naomi Osaka, powered past Maria Sakkari 7-6(3), 6-2 to level the Group B contest at 1-1 after Stefanos Tsitsipas had beaten American Frances Tiafoe 6-3, 6-7(3), 6-3.</p>.<p class="bodytext">The 37-year-old, who had both ankles strapped and required medical attention in her singles match, then combined with Tiafoe but could not overcome Sakkari and Tsitsipas who won the mixed doubles rubber 4-1, 1-4, 4-2 to seal the tie.</p>.<p class="bodytext">"It's great to be back out in match day, and it's great to be back out here," said Williams, who will be chasing a record-equalling 24th Grand Slam title at the Australian Open next month.</p>.<p class="bodytext">Williams made several unforced errors early on but overpowered her opponent with 13 aces and 29 winners, claiming two breaks en route to a comfortable win.</p>.<p class="bodytext">"It was my first match back, she played unbelievable. Maria is super young and such a good player. I was making a lot of errors. I was like, 'It's OK, it's your first match and you'll get better'. I just kept trying to think that."</p>.<p class="bodytext">Defeat left six-times winners US at the bottom of the group ahead of Tuesday's meeting with holders Switzerland, who thumped Britain on Sunday.</p>.<p class="bodytext">Roger Federer and Williams, holders of a combined 43 singles Grand Slam titles, will face each other for the first time on Tuesday when they feature in the mixed doubles match alongside partners Belinda Bencic and Tiafoe.</p>.<p class="bodytext">Local media have described the clash as the most anticipated match involving men and women since 1973's "Battle of the Sexes" which saw 39-times major winner Billie Jean King beat former men's world number one Bobby Riggs in an exhibition match.</p>.<p class="bodytext">"It's exciting for both of us and I hope a lot of tennis fans tune in and watch it," Federer said on Sunday.</p>.<p class="bodytext">"I admire everything she's done on and off the court, we're both fierce competitors and we always want to win."</p>
<p class="title">Serena Williams made a winning return to competitive action at the Hopman Cup on Monday but could not prevent the United States from losing 2-1 to Greece in their opening round-robin match.</p>.<p class="bodytext">Williams, playing her first competitive match since losing the US Open final to Naomi Osaka, powered past Maria Sakkari 7-6(3), 6-2 to level the Group B contest at 1-1 after Stefanos Tsitsipas had beaten American Frances Tiafoe 6-3, 6-7(3), 6-3.</p>.<p class="bodytext">The 37-year-old, who had both ankles strapped and required medical attention in her singles match, then combined with Tiafoe but could not overcome Sakkari and Tsitsipas who won the mixed doubles rubber 4-1, 1-4, 4-2 to seal the tie.</p>.<p class="bodytext">"It's great to be back out in match day, and it's great to be back out here," said Williams, who will be chasing a record-equalling 24th Grand Slam title at the Australian Open next month.</p>.<p class="bodytext">Williams made several unforced errors early on but overpowered her opponent with 13 aces and 29 winners, claiming two breaks en route to a comfortable win.</p>.<p class="bodytext">"It was my first match back, she played unbelievable. Maria is super young and such a good player. I was making a lot of errors. I was like, 'It's OK, it's your first match and you'll get better'. I just kept trying to think that."</p>.<p class="bodytext">Defeat left six-times winners US at the bottom of the group ahead of Tuesday's meeting with holders Switzerland, who thumped Britain on Sunday.</p>.<p class="bodytext">Roger Federer and Williams, holders of a combined 43 singles Grand Slam titles, will face each other for the first time on Tuesday when they feature in the mixed doubles match alongside partners Belinda Bencic and Tiafoe.</p>.<p class="bodytext">Local media have described the clash as the most anticipated match involving men and women since 1973's "Battle of the Sexes" which saw 39-times major winner Billie Jean King beat former men's world number one Bobby Riggs in an exhibition match.</p>.<p class="bodytext">"It's exciting for both of us and I hope a lot of tennis fans tune in and watch it," Federer said on Sunday.</p>.<p class="bodytext">"I admire everything she's done on and off the court, we're both fierce competitors and we always want to win."</p>