The Swiss maestro sent 22-year-old Canadian Milos Raonic packing with a 6-4 7-6 6-2 masterclass under the lights of Rod Laver Arena on Monday, providing a blueprint for Williams ahead of her all-American quarter-final against teenager Sloane Stephens.
The 31-year-old Williams appeared in little need for tips, however, as she demolished Maria Kirilenko 6-2 6-0 earlier in the evening session to notch her 35th appearance in the last eight of a grand slam.
U.S. Open champion Andy Murray, who like Federer has not lost a set at Melbourne Park, clobbered shattered 14th seed Gilles Simon 6-3 6-1 6-3 to go to within three wins of back-to-back grand slam titles.
Needing a measly 57 minutes to dispatch the 14th-seeded Russian, Williams will face another woman in a hurry in 19-year-old Stephens.
The wise-cracking up-and-comer has been touted as an heir to the 15-times grand slam champion Williams and burnished her credentials with a poised 6-1 3-6 7-5 win over Serbia's Bojana Jovanovski in the afternoon sun at Hisense Arena.
Williams has been branded a mentor to the impressive Stephens, whom she beat in the leadup tournament in Brisbane but with a sixth title at Melbourne Park on the line, she quickly backed away from the role.
"I don't know. I mean, I would need a better definition of the word 'mentor'," Williams told reporters.
"It's hard to be a real mentor when you're still in competition."
Federer smacked down Australian upstart Bernard Tomic in three sets in the previous round, and was in no mood to emulate defending champion Novak Djokovic, who was stuck on center court for five hours the previous night before wearing down Swiss Stanislas Wawrinka.
Federer drew the big-serving Canadian's sting in a tight second set and romped to victory with 34 sparkling winners to set up a quarter-final with France's Jo-Wilfried Tsonga.
"I just try to go out there and play my best, regardless if they're young or not," said Federer, bidding for a fifth title at Melbourne Park. "But I get a lift, as well, in terms of energy playing against those kind of guys."
The 13th seed Raonic, tipped to trouble the heavyweights in years to come, played with a local anaesthetic to ease the pain of a foot injury, and nearly pulled out of the match.
"So I didn't really get a chance to hit before my match ... (He) just sort of swept me off the court," Raonic said.
Britain's Murray derived little joy from his win over Simon, with the Frenchman reduced to a staggering wreck in the closing stages.
Simon had been exhausted by compatriot Gael Monfils in a five-set marathon in his previous match and could do little more than stick out his racket and hope as he slumped to his 10th straight loss to the Scot.
The monotoned Murray has made an art form of sounding blase about rollicking victories, but struck a new depth of melancholy as he lamented the lack of competition at his post-match media conference.
"It was kind of tough. A tough situation for both players - more obviously for him... It didn't feel like that competitive," said Murray, who will face another Frenchman in surprise package Jeremy Chardy.
Four Frenchmen advanced to the last 16 at Melbourne Park for the first time since 1998 and 36th-ranked Chardy kept the flag waving with a 5-7 6-3 6-2 6-2 win over 21st seeded Italian Andreas Seppi.
That secured Chardy's maiden grand slam quarter-final and ensured France would have two men in the last eight, with seventh seed Tsonga grinding down ninth-seeded compatriot Richard Gasquet 6-4 3-6 6-3 6-2.
Unfancied and unseeded, the scruffy-bearded Chardy stunned sixth seed Juan Martin del Potro in his previous match and said he had nothing to lose against Murray, who he beat in straight sets in Cincinnati last year after losing all four of their previous matches.
"(It's) just like a dream," the thrilled 25-year-old told reporters. "I know I can beat everybody. So when I feel confident, I believe in me. Against Del Potro, I played a very good match. So it was good for my head."
World number one Victoria Azarenka was back at her ruthless best in a 6-1 6-1 demolition of 47th-ranked Russian Elena Vesnina after being taken the distance in her previous match by American Jamie Hampton.
She faces a stiffer challenge in the quarter-finals against another Russian in Svetlana Kuznetsova, who sent 10th seed Caroline Wozniacki spinning out of the tournament and out of the top 10 when the next round of rankings are released.
Kuznetsova, the 2004 U.S. Open champion and winner at Roland Garros in 2009, spent much of last year on crutches with a knee injury, and was thrilled to secure her third quarter-final at Melbourne Park.
"If you had asked me before coming to Australia I would have laughed, definitely," Kuznetsova said of her surprise run.