Resplendent in a pair of pink and black two-toned sneakers, Federer captured a break early in each set, while his 40th-ranked opponent never had a look at his serve and surrendered their 20th tour clash in just under two hours.
The blue-collar Davydenko offered stiffer resistance than Swiss maestro's first-round opponent Benoit Paire, but Federer stayed cool on a balmy evening at Rod Laver Arena and belted an ace to close out the match.
Federer, chasing an 18th major title in Melbourne, needed a fraction under two hours to beat Davydenko and was quick to warn the Australian that he was probably fitter than 10 years ago.
"I'm much more experienced today. I know what I can expect from myself in terms of my level of play early on," the second seed said.
"I'm much stronger today physically clearly so I can always rely on that as well, extend the rallies, so don't have to be worried about that."
Federer will continue his bid for an 18th Grand Slam title and fifth at Melbourne Park against Australia's Bernard Tomic.
The 31-year-old Federer was a paragon of Swiss neutrality as he looked ahead to the match, but was goaded into reminding the plucky 20-year-old of the gulf between the players.
"Look, I have so much more experience than him," Federer said, when asked to clarify comments about aiming to dominate Tomic physically.
"Last year I reached my thousandth match on tour. That's what I meant. I know how hard a five-setter can be. I know how intense a night session can be and all these things.
"Whatever that means, length of rally, length of match, intensity, I've been there. That could potentially help me, but it could also not help me.
"We'll see how it goes. But he's done a really nice job today, for instance, in the heat."
Despite Federer's words Tomic blew seven match points in his clash with Germany's Daniel Brands but sealed a hard-fought 6-7 7-5 7-6 7-6 victory on the eighth to become the host nation's last player standing.
The bad boy of tennis Down Under had two chances to secure victory at Rod Laver Arena on 120th-ranked Brands' serve at 6-5 in the fourth set.
Brands saved them both, and another five in the decisive tie-break, before Tomic closed it out 10-8.
"I definitely got my arse kicked (by Federer) both times," said 43rd-ranked Tomic, who was beaten by the Swiss maestro in the fourth round of last year's tournament and later in the year at Cincinnati.
But despite that and his wobbly second round match, the much-vaunted Australian said he felt it was the "perfect" time to play Federer.
"I think, you know, I've got a good attitude to win," said Tomic, who won his first ATP title in Sydney in the lead-up after upsetting a jet-lagged Novak Djokovic at the Hopman Cup in Perth.
"I've beaten a lot of good players over the last past two weeks, especially Novak. I think I can do it.
"I'm ready. I mean, I'm not going to say, you know, I don't have the belief. I do have the belief now. It's possible. I showed that in Perth, that you can beat these players."
Frenchman Jo-Wilfried Tsonga dealt with the sweltering heat to advance with a 6-3 7-6 6-3 victory over Go Soeda.
Tsonga looked to be wilting in cauldron of Margaret Court Arena when Soeda was 5-3 up and serving for the second set but the seventh seed recovered to slap down the Japanese and complete a straight-set win.
Tsonga, losing finalist here five years ago, was not happy with his performance but was not about to blame the heat.
"You have to deal with it. That's it," he said.
Tsonga next faces Blaz Kavcic of Slovenia, who beat Australian wildcard James Duckworth after the pair slugged it out for four hours and 52 minutes on court three in ferocious heat in the middle of the day before Kavcic won 3-6 6-3 6-4 6-7 10-8.
"Total physical collapse after the match," the Slovenian Tweeted lightheartedly along with a picture of him receiving medical treatment in the locker room. "Feeling quite happy though, just don't know, because of my win or morphine."
There were wins for seeds Juan Martin Del Potro, Richard Gasquet, Marin Cilic, Milos Raonic, Gilles Simon, Philipp Kohlschreiber and Andreas Seppi but the outer courts were again the place to go for upsets with Lithuanian Ricardas Berankis hammering 25th seed Florian Mayer 6-2 6-3 6-1 on court six.
Berankis's victory means he will be Andy Murray's next opponent and the convincing nature of his win over Mayer indicated that he might prove trickier for the Scot than Joao Sousa.
Spanish 30th seed Marcel Granollers also went out, losing to France's Jeremy Chardy in four sets and his compatriot Gael Monfils joined him in the last 32 after he survived an attack of the jitters to beat Yen-Hsun Lu of Taiwan 7-6 4-6 0-6 6-1 8-6.
Monfils, unseeded as he makes his way back from a long injury absence, double-faulted on four successive match points before finally clinching victory in just under four hours.
"It was a bit crazy," Monfils said in a courtside interview. "It was like, 'I need to hit an ace because I know it's going to be a double-fault for sure. It was weird.
"I think I got a bit lucky in the end."
At one stage in the third set, Monfils looked to be struggling for breath in sweltering temperatures that had tipped 40 degrees Celsius earlier in the day.
But after gathering himself in the fourth set, he held on to win the fifth and now plays another Frenchman, 14th seed Simon, for a place in the last 16.
Monfils was ranked as high as seventh in 2011 but missed large chunks of the 2012 season with a right knee injury and has slipped to 86th in the rankings.
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