ESPN 2009 Australian Open

MELBOURNE, Australia -- The chase for a 14th Grand Slam is still alive for Roger Federer at the Australian Open, but there's also cause for concern after his 4-6, 6-7 (4), 6-4, 6-4, 6-2 win over Tomas Berdych in the fourth round.

The setup was not an ideal one for the three-time Melbourne champion -- an afternoon match after playing at night in his previous two rounds, and an opponent with an enormous but erratic game.

Every player feels a bit apprehensive when stepping out to face the big bomber Berdych. It's the dread of the unknown. The 23-year-old Czech is widely known as a fainthearted competitor, but when everything is working he can be virtually impossible to stop.

Federer got a taste of both versions today, going down two sets before weathering the storm and coming through in five. But relieved as he was, Federer must also be aware that the turnaround did not come off his own racket: Had Berdych not choked in typical fashion in the middle of the third set, chances are the two would have rolled the dice in another tiebreaker, and it could well have been over in three sets.

What will happen if one of Federer's opponents next week is not quite as obliging? His quarterfinal opponent will be the rising young Juan Martin del Potro, possibly followed by Novak Djokovic, and Andy Murray or Rafael Nadal in the final.

But for now, Federer has survived, recording his first comeback from two sets down since the 2005 Miami final against Nadal. "It hasn't happened in a long time, so I hope it's a good omen," said Federer.

It was obvious that Berdych was going to be formidable from the very first game, when he blasted two forehand winners to break Federer's serve off the bat before securing a second break to go up 4-1.

Berdych began the match doing almost everything he tends to do on such occasions: finding the range on his first serve, hitting monster groundstrokes and charging his 6-foot-5 frame regularly toward the net.

Federer, meanwhile, was unable to do most of what he usually does. He looked flat; his forehand lacked zing; and there were none of those little explosive bursts of speed so vital for capturing the offensive during a rally.

Federer's tendency to push the return back when facing big servers was doing him no favors early on -- the Czech simply gobbled them up, putting 72 percent of his first serves in play and winning 78 percent of those points.

"I didn't want to start too aggressive from the first game, but it looks like that I got the chance from the first point already," said Berdych. "Then I just took the chance and was trying to pushing him as hard as I can."

After his startling beginning, Berdych began rolling like a tank, dictating the points and crushing his opponent's attempts at resistance. When the Swiss broke back to 4-2, Berdych shrugged it off, eventually serving out the set to love.

But the Czech's first-serve percentage dropped off during the rest of the match, and this would slowly begin to have an impact. Federer broke immediately to begin the second set, but lost the advantage at 2-0 thanks to a double fault at 15-30 followed by a big Berdych return.

The set was settled in a tiebreaker, and Berdych took charge at 4-4 by drilling a deep return off a short second serve from Federer and then taking advantage of a floating return to run Federer side to side and put away the volley. A huge forehand secured Berdych a two-set lead a few seconds later.

Shock settled over the pro-Federer crowd in the stadium, but Federer had known coming in that this was a possibility.

Berdych upset the then-No. 1 in the third round of the Athens Olympics, and even though Federer has won all seven matches since, he was wary. "I know the danger of playing Tomas," said Federer. "He's top-3, top-5 guy [for] most powerful shots in the game. You combine serve, forehand and backhand, it's incredible the pace he gets with little effort."

But Federer also knew that Berdych has a tendency to crack, and did not give up, even though his efforts to establish some kind of momentum were frustrated again early in the third. Twice he broke; twice Berdych broke right back.

Then came the proverbial "vital seventh game," and sure enough, the match took a hairpin turn.

Serving at 3-3, Berdych ran the gamut of unforced errors -- forehand, backhand, volley -- and finally, he grotesquely botched an overhead just a few feet from the net.

It was the end -- and because this was Berdych, everyone knew it was the end. Physically, he hung around 'til the finish, even earning a break point when Federer served for the match at 5-2. But psychologically, it was obvious the magic was gone.

As Berdych's flat, powerful groundstrokes began to lose their sting, Federer grew bolder. Soon he was coming up with big serves at will, and finished the match with two consecutive aces.

It may be an omen, but of what? He went five sets with Igor Andreev in the fourth round of the U.S. Open and ended up winning the whole thing. But a mononucleosis-affected Federer also went five against Janko Tipsarevic in the third round here last year, and he eventually lost in the semifinals.

But one thing is for sure: His Grand Slam chase just became a lot more interesting.

Kamakshi Tandon is a freelance tennis writer for ESPN.com.