Williams dealt with Russian Maria Kirilenko as though she was running late for a nine o'clock movie, motoring into the last eight for the eighth time in Melbourne with a 6-2 6-0 centre-court mauling on Monday night.
Extraordinarily, the 15-times grand slam champion landed almost 90 per cent of first serves and raised her tournament tally to a championship-best 30 aces in swatting aside Kirilenko in 57 minutes.
"I thought I played really well," Williams said.
"I didn't expect to come out and play so well tonight. I was like `wow'. I saw I had like 95 per cent of first serves in the first set and I thought: `Who is this girl?'
"It's not me normally."
The victory was Williams' 40th from her past 41 matches and she will be a raging favourite on Wednesday to end the career-best run of 19-year-old Stephens, who idolises her fellow American.
"I think she's playing great," Williams said of her challenger.
"We played just two weeks ago in Brisbane and she played really unbelievable; I think she has incredible talent.
"I actually admire her as well. It will be a really tough match for me."
Stephens qualified for her maiden grand slam quarter-final with a 6-1 3-6 7-5 win over Serbian Bojana Jovanovski but will need to reverse her 6-4 6-3 loss to Williams in Brisbane a fortnight ago to keep her dream campaign going.
The fast-rising world No.25 was giving Williams due respect but also refusing to rule out the possibility of causing a grand slam boilover.
"She's obviously one of the greatest players to ever play the game," Stephens said.
"Without all that, it's still a tennis match. You have to go out and play your game, no matter what.
"Without the titles, with the titles, it's still a tennis match. The court's the same size.
"You're still playing a regular person across the net. You've just got to go out and play."
While Stephens will be contesting her first, 31-year-old Williams will line up for her 35th grand slam quarter-final.
"It's awesome," the third seed said.
"I've had a great career, especially here in Australia.
"I love it here, so I look forward to a good match."