MELBOURNE, Australia - American Brian Baker's hopes of a fairytale run at the Australian Open were ended in the cruellest of fashions on Wednesday when he was taken off court in a wheelchair after suffering a serious knee injury.

The 27-year-old, who returned in 2012 after seven injury-plagued years off the professional circuit, had won the first set of his second round match against compatriot Sam Querrey when he suffered the injury.

"I didn't see what happened," Querrey told reporters. "I hit a ball, and then he hit a ball long. I was looking at the ballkids to grab balls for my serve, and then I looked back and he was on the ground.

"And then just asking him, he said he kind of just felt his knee almost buckle and kind of heard like a pop or a snap. He didn't know if it was bones or a tear, but he couldn't straighten it, couldn't walk.

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"I feel awful for him."

After receiving treatment on his right knee, Baker was wheeled away with what broadcaster ESPN reported was a torn lateral meniscus, which will require surgery and four months on the sidelines.

Runner-up at the French Open juniors in 2003, Baker was working his way up the senior rankings in 2005 when he first felt an injury in his left hip, which required surgery.

That began a nightmare run of two left hip surgeries, a right hip operation, hernia surgery and right elbow surgery which, with the exception of a couple of matches in 2007, kept him off the tour until 2011.

"He's the last person that deserves anything like that with his five or six surgeries already," added Querrey.

"He does everything right, treats his body great, just trying to come back, and then something like that happens, it's just so unlucky."

Baker gave it one final go last year and went from world number 456 to 57 at the start of this year's first grand slam, taking in a run to the last 16 as a qualifier at Wimbledon on the way.

His victory in the first round at Melbourne Park against Alex Bogomolov Jr of Russia on Monday was his first at the Australian Open and he had hoped to get back into the top 50 in the world by May.

"In my mind he's a top 50 player and he can beat guys who are top 20, top 10," Querrey, the 20th seed, said.

"I think if he can heal quickly ... I think he can get right back where he is right now. He's talented, he's good enough."

Querrey, the sole American men's seed this year in the absence of injured compatriot John Isner, will now meet Swiss Stanislas Wawrinka for a place in the fourth round.

Top-ranked Djokovic cruises

Novak Djokovic's campaign for a hat-trick of Australian Open titles shifted up a gear on Wednesday, as he demolished American Ryan Harrison 6-1 6-2 6-3 to charge into the third round.

The steely-eyed Serb warmed up with a workmanlike performance in his opener against Frenchman Paul-Henri Mathieu, but was at his devastating best in a 91-minute rout of the 62nd-ranked Harrison.

Bullied on the baseline and broken early in each set, the 20-year-old American scrambled hard to make a contest under the lights at Rod Laver Arena, but surrendered the match when his opponent ripped a searing forehand down the line.

Djokovic will continue his bid for a sixth grand slam title, and fourth at Melbourne Park against Czech veteran Radek Stepanek.

No. 24 seed Janowicz survives after on-court tantrum

Poland's Jerzy Janowicz could not afford to come to the Australian Open last year but on Wednesday he made a real mark on the grand slam with a spectacular tantrum followed by a brilliant comeback from two sets down.

The 24th seed exploded with rage over a line call in the tiebreak at the end of the 79-minute first set against Somdev Devvarman, roaring his displeasure, hitting the umpire's chair with his racket and throwing his water bottle across court.

At one stage, the 22-year-old collapsed to his knees in frustration with his forehead touching the playing surface on court eight.

"I was really worried about his voice," said Indian Devvarman. "He was really yelling at the top of his lungs and I said, 'Dude, calm down'."

Devvarman took the tiebreak 12-10 to win the set and, at the changeover, Janowicz again argued his case with Croatian umpire Marija Cicak before making the point more forcefully with his racket.

Janowicz regained his composure and was back on his knees in celebration 161 minutes later after a 6-7 3-6 6-1 6-0 7-5 victory that secured him a third round tie against Spanish 10th seed Nicolas Almagro.

"The umpires, they're making so many mistakes ... this was the moment when I went nuts, otherwise the rest of the match I was pretty calm," said Janowicz, who reached the final of the Paris Masters last November.

"Sometimes it happens like this. You can't control your emotions all the time. This was a really big point for me. We played this set for more than an hour and 10 minutes, so this was a really important point for me."

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India's sole remaining representative in the single's draws, Devvarman raced away with the second set while the Pole was still regaining his composure.

Despite tallying 88 unforced errors over the match, Janowicz struck back by ramping up his serve and unleashing his forehand to level up the match at two sets all.

The hour-long deciding set was closer, with the players exchanging service breaks before the Pole secured the victory with another blistering forehand return for his 91st winner of the match.

"Every win is really nice," he said. "But if you are losing two-love and you come back, that gives you a little bit more confidence."

Janowicz's run to the final in Paris and finding a sponsor helped ease his parlous financial state but he still hoped he would avoid a fine for his outburst.

"I got a warning only because I was shouting," he said. "I didn't say anything bad, so I hope I will not have to pay."

Devvarman, who reached a career-high 62nd in the world in July 2011, has slipped to 551 after missing most of the 2012 season with a shoulder injury.

He dismissed the idea that Janowicz might have staged his tantrum to try and put him off and suggested the Pole would cause problems for other players this year.

"He played incredibly well and started going for his shots and they fell in," he said. "I let it go but he also took it away from me.

"He's got so many weapons but what's really dangerous about him is you literally don't know what he's going to do next."

Nos. 4, 5 seeds Ferrer, Berdych advance

With defending champion Novak Djokovic not playing until the last match on Rod Laver Arena and the two other members of the men's 'Big Four' not back on court until Thursday, there was a somewhat flat feeling to the start of day.

Radwanska was followed on Rod Laver Arena by men's fifth seed Tomas Berdych, who wrapped up a 6-2 6-2 6-4 hammering of Frenchman Guillaume Rufin with his eighth ace after exactly two hours.

David Ferrer, seeded fourth in the absence of Nadal, was playing out on Margaret Court Arena and required 38 minutes longer to dispatch dogged American lucky loser Tim Smyczek 6-0 7-5 4-6 6-3.

Berdych is the likely quarter-final opponent for Djokovic, while Ferrer is seeded to play the Serbian world number one in the semi-finals.

Japan's Kei Nishikori said he had brushed off the knee injury that forced him to withdraw from the Kooyong warm-up after his 7-6 6-4 6-1 victory over Argentina's Carlos Berlocq on court three.

"It's getting better," the 16th seed said. "And I didn't feel any pain today. Just the hot conditions bothered me a little, but otherwise fine."