And the 20-time grand slam victor, who will attempt to win a third straight Australian Open title later this month, was satisfied with where his form and fitness is at.
Williams is now playing Bencic in the women's singles of the Group B match before the eagerly awaited mixed doubles takes place.
It's been billed as the most anticipated match involving men and women since 1973's "Battle of the Sexes" which saw 39-times major victor Billie Jean King beat former men's world No 1 Bobby Riggs in an exhibition match.
Leading 4-1 in the first set, Williams looked set to be cruising to a comfortable victory until her 21-year-old opponent hit back to win the next five games and take the opener.
As it turned out, the tie was decided by the mixed doubles, after both Federer and Williams won their earlier singles matches.
There has always been a debate over whether Roger Federer or Serena Williams is greater but the Swiss added another feather to his cap in what's likely to be the only meeting between the pair during their professional careers.
"You know I've been training offseason to be ready for Roger, so not sure how I'm going to do but we'll see", Williams said.
Paine admits that Australia need Smith, Warner
Meanwhile, India will be looking to build on the momentum and will leave no stone unturned to make it 3-1 at the SCG. Border heaped praise on India's pace unit, saying: "It's as a good an Indian bowling attack as I've ever seen".
Arsenal boss Emery’s message to outgoing Ramsey
Ramsey to Juventus will be a cool deal only if they could pull through for the price, and would add extra boost to their defence. It was also disclosed that the former Cardiff City player will sign a four-year contract worth €8m on a yearly basis.
Djokovic downs SA's Anderson in Abu Dhabi final
What does the Russian think of Djokovic's level after he played him in Friday's semi-finals. Honestly this is a flawless way to start the season.
"I guess what you're seeking here is confirmation to see is everything there that you thought there was, or is there any fixing still to be done in the coming weeks".
"It's great to back out here, I love playing Down Under here in Perth and in Australia, some of my best memories are here" Williams told Channel Nine after the match.
"I really can not imagine how".
Federer beat Cameron Norrie, the British No 2, 6-1, 6-1 in 57 minutes as Switzerland defeated Great Britain 3-0. Federer has 20, Williams 23. The winners of each group will contest Saturday's final.
While the focus was on the two icons of the sport, the most entertaining exchange came early in the second set with Federer and Tiafoe both tagging each other.
The pair battled it out for over two hours in their first round match before Venus broke through in the sixth game of the decider to set up victory.
"I don't know her that well", he said. Williams then overcame a case of the first-set wobbles to post a 4-6, 6-4, 6-3 success over Belinda Bencic, levelling the tie.