London:
Defending champion Roger Federer edged into the third round at Wimbledon with a 6-3, 6-7 (4/7), 6-4, 7-6 (7/5) win over Serbian qualifier Ilija Bozoljac on Wednesday.
Federer did just enough to see off the unheralded Bozoljac, ranked 152nd in the world, but once again the air of invincibility that usually surrounds the six-time Wimbledon champion was completely absent.
The top seed had made heavy weather of his first round win over Colombian Alejandro Falla and this was no different as Federer struggled to maintain any momentum.
Although Federer's phenomenal record at Wimbledon was enough to guarantee him the number one seeding, ahead of world number one Rafael Nadal, he has arrived in south-west London with serious questions over his form.
By his own high standards 2010 has been disappointing year for Federer, who has failed to win any of his seven tournaments since beating Andy Murray in the Australian Open final in January.
Federer' run of 23 successive grand slam semi-final appearances was snapped at the French Open and he even lost for just the second time in 78 matches on grass when Lleyton Hewitt beat him in the final at Halle earlier this month.
There was little sign of an improvement in his form as the Swiss star stumbled to an error-strewn victory over Falla in the first round on Monday.
He had trailed by two sets and Falla even served for the match in the fourth set before Federer finally rallied to a win he hoped would mark a change in his luck.
Initially, it seemed that would be the case as Federer missed two early break points but was then gifted another which he seized in the seventh game for a 4-3 lead.
That was enough to take the first set. But Federer, who had surprisingly been shunted out to Court One for this match, then slipped back into the erratic form that haunted him for much of the Falla tie.
Bozoljac has never been past the second round of a grand slam and has attracted as much interest in Serbia for his relationships with a string of models than anything he has achieved on the tennis court.
But he was relishing his moment in the spotlight and kept Federer at bay with some big-serving in a second set which went to a tie-break.
Federer so often goes for the kill at that point but he was strangely timid and allowed his inexperienced opponent to dictate the tempo to such an extent that he took the breaker.
Federer needed to snap out of his lethargy and he gradually found just enough rhythm to win the third set - the key moment coming when Bozoljac double-faulted on break point at 2-2.
The world number two continued to confound expectations that he would cruise through.
He failed to convert two break points at 2-2 in the fourth set and had to produce two big serves and a superb winner on the run to deny Bozoljac a break of his own in the next game.
Another tie-break was needed to settle the set and an exchange of mini-breaks sent the tension rising.
To his credit, Federer battled gamely against his own erratic play and came up with the big points when he needed him.
Hitting deep to Bozoljac's baseline, he forced an error from the Serbian on match-point that finally sealed an unconvincing win.