Serena Williams beat Maria Sakkari 7-6(3), 6-2 in their Hopman Cup singles encounter - but the US lost the tie to Greece following the mixed doubles decider.
The 23-time Grand Slam champion reported some soreness in her ankle, but hit 13 aces and 29 winners en route to victory.
"It’s great to be back out in match day, and it’s great to be back out here," she said after the match.
"I love playing in Australia. Some of my best memories are here. It was my first match back (today), 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."
Williams later partnered up with Frances Tiafoe for the mixed doubles against Sakkari and Stefanos Tsitsipas, which the Greek pair won 4-1, 1-4, 4-2.