Federer was out of sorts throughout the match against a player ranked 151 places below him. PHOTO: AFP
Playing his first match of the year after receiving a first round bye, world number two Federer had to come from a set and a break down to overhaul Millman 4-6, 6-4, 6-3 in just over two hours.
Federer was out of sorts throughout the match against a player ranked 151 places below him, making 38 unforced errors — most of them in the opening set-and-a-half.
Millman, on the other hand, played some brilliant tennis, spurred on by the emotion of playing in front of family and friends on his home court.
Two years ago he took a set off Britain's Andy Murray at the Brisbane International before fading away.
Millman was out of the game for 12 months from May 2013 with a shoulder injury and has only played lower level Challenger tournaments since then.
He has won just three matches on the main ATP Tour in his career, two of those in Brisbane, and has US$261,000 in prize money, compared with Federer's $88.6 million.
But for much of the match there appeared little difference between the two as Millman lifted and Federer struggled to find his touch.
Millman, 25, stunned the capacity crowd at Pat Rafter Arena when he broke Federer to take the first set, then broke again to lead 3-1 in the second.
But Federer noticeably lifted a level, breaking straight back before breaking Millman's next serve to force a decider.
The Swiss maestro took advantage of his tiring opponent to ease away with the third set in 37 minutes.
"I was under a lot of pressure — I think I got quite lucky in the second set," said Federer.
"He was playing great tennis until the last couple of games.
"It's the start of the season — I never know what to expect. I was just happy to win."
Federer now plays another Australian wildcard, James Duckworth, in the quarter-finals following his 4-6, 7-6 (7/5), 6-3 win over Finland's Jarkko Nieminen.
Earlier, Canada's Milos Raonic fired off 17 aces in his 6-3, 6-4 win over Mikhail Kukushkin of Kazakhstan.
Raonic ended the year ranked eighth in the world and, along with Grigor Dimitrov and Kei Nishikori, is seen as one of the men most likely to end the dominance of Federer, Novak Djokovic and Rafael Nadal.
He said he had worked on all aspects of his game during the off-season, which stood him in good stead heading into the year's first Grand Slam in Melbourne in just over a week.
"I feel good, I've put a lot of work in technically and on a lot of things, so I feel better as a tennis player — I feel much stronger and fitter," he said.
"I also spent a lot of time sort of discussing and consulting with my team about the mental side, what I need to do to make the next step forward, especially in the big events."
He next takes on fellow big server Sam Groth in the quarter-finals after the Australian won 6-4, 6-7 (2/7), 7-6 (7/3) over Polish qualifier Lukasz Kubot.
Sharapova cruises, Ivanovic struggles
Top seeds Maria Sharapova and Ana Ivanovic booked their places in the semi-finals of the Brisbane International in vastly contrasting fashion on Thursday.
While world number two Sharapova cruised past Spaniard Carla Suarez Navarro 6-1, 6-3, Ivanovic was forced to recover from a horror start before edging Kaia Kanepi 4-6, 6-4, 6-3.
Sharapova was in ominous form on Pat Rafter Arena as she overpowered Suarez Navarro in just 68 minutes.
The top seeded Russian hit 32 winners in the match, 20 of those from forehands, as she set up a semi-final against unseeded Ukranian Elina Svitolina.
Sharapova was all business on Thursday against a player who beat her in 2014.
"I'm always a little bit aware of girls that I lose to. I certainly know that she's capable of playing really well, plays defence great and makes you hit a lot of balls," Sharapova said.
"Especially on a slower court like here, you just don't want to give her that much time.
"I thought I did a good job of that — maybe made a little bit too many unforced errors in the beginning, but then got a good rhythm and finished strong."
Svitolina earlier came from a set and 0-3 down to upset third-seeded German Angelique Kerber 4-6, 7-5, 6-3.
The 20-year-old was staring a second round exit in the face when Kerber had a break point to go ahead 4-0 in the second set.
But the German hit a simple forehand long and Svitolina began to claw her way back.
"I was not really thinking about the score, I was just trying to play every single point as the last one," she said.
"That was the only thing I was thinking about, to find my rhythm to play, just rally with her."
Kanepi, the 2012 Brisbane champion, came out blazing in her quarter-final against Ivanovic.
She broke the Serbian's first three service games to lead 5-0 and 40-30 before faltering, surrendering her next two serves.
Ivanovic came storming back but Kanepi at last managed to hold to take the first set in 43 minutes.
However, the momentum had swung ever so slightly to the second seed, who levelled the match in a tight second set, then broke Kanepi once in the third to set up a semi-final against American Varvara Lepchenko.
"I was feeling the ball well at the start but I just missed some easy points and some put-aways," Ivanovic said.
"But I'm happy with the way I fought back and nearly got there. I was happy with my composure in the second.
"It was a great test, not only physically but also mentally."
Lepchenko ended the run of Alla Kudryavtseva 7-5, 7-5.
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