Serena Williams went ahead with her preparations for the Australian Open after beating British player Katie Boulter on Thursday to continue her Hopman Cup without a defeat.
Williams had regressed after a strong start, but she won 6-1, 7-6 (2) in the 78-minute game, with the United States and Britain tied in the second set.
But Britain won the draw when Poulter and her partner Cameron Norrie had a comeback 3-4 (2), 4-3 (4) and 4-1 victory over Williams and Frances Tiafoe in the mixed doubles.
Williams's hopes of winning the third Hopman Cup title ended after the United States was eliminated after losing to Greece and Switzerland led by Federer.
"It was definitely good to play three singles matches here, not to mention the mixed," she said after her singles match.
Serena, currently ranked 16th, is looking to win her 24th singles title at Melbourne's Grand Slam championships in September.