Shanghai - Roger Federer survived a big scare on Thursday to reach the Shanghai Masters quarter-finals and guarantee a 300th career week as world No 1 as Novak Djokovic and Andy Murray showed ominous form.
The Swiss 17-time Grand Slam champion came into the match against compatriot Stanislas Wawrinka with an enviable 11-1 head-to head record but struggled to impose himself and was forced to dig deep before winning 4-6, 7-6 (7/4), 6-0.
In a gripping contest lasting nearly two hours, Wawrinka, who teamed up with his illustrious compatriot to win Olympics doubles gold in 2008, broke Federer in the seventh game to lead 4-3 and sealed the first set.
Out-of-sorts Federer, 31, continued to struggle in the second set as the pair swapped breaks of serve and was in desperate trouble when Wawrinka earned a break point for a 5-4 lead, which would have left him serving for the match.
But the Swiss great dodged that bullet and stayed strong in a nerve-jangling tie-break to level the match and immediately broke his 27-year-old countryman at the start of the third set as momentum shifted decisively in his favour.
A dejected Wawrinka failed to win another game as Federer wrapped up the third set 6-0.
Earlier, Serbian second seed Djokovic looking to wrestle the world No 1 ranking from Federer barely broke sweat against Spain's Feliciano Lopez, wrapping up a straightforward 6-3, 6-3 victory in front of enthusiastic fans.
In-form Djokovic, fresh from his third China Open title in Beijing on Sunday, struck 12 aces and took advantage of some below-par serving by the left-handed Lopez, breaking him three times.
"I'm not very well known around the Tour for big serving," said Djokovic, 25. "But so far in this tournament, and also in Beijing, it has been working very well for me.
"It has been giving me a lot of free points, a lot of confidence into the matches."
US Open champion Murray, 25, proved far too strong for Ukraine's Alexandr Dolgopolov, serving consistently well and seizing on five out of six break points to win 6-2, 6-2 in just 57 minutes.
It was the first match of the tournament for the Scot, who had a walkover into the third round. The top eight seeds received a first round bye.
"I think I did a decent job," said Murray. "It's very, very different conditions to last week. I think you can see by some of the results here, the guys that have come from Beijing have adapted to the conditions much, much quicker."
Fifth seed Jo-Wilfried Tsonga, currently in line to secure the last singles berth in the elite eight-man field at the ATP World Tour Finals, beat Marcos Baghdatis of Cyprus 6-2, 7-6 (7/2) in a contest containing eight breaks.
Czech fourth seed Tomas Berdych, sixth in the Race to London, set up a quarter-final meeting with Tsonga after fending off a barrage of 17 aces from American Sam Querrey to win 6-2, 6-7 (3/7), 6-4.
Radek Stepanek of the Czech Republic upset eighth seed John Isner of the United States in three sets while 10th seed Marin Cilic of Croatia beat Spain's Fernando Verdasco, also in three sets.
As the season enters its final few weeks, Federer, Djokovic, Murray and the injured Rafael Nadal have already qualified for the ATP World Tour Finals. There are four places still up for grabs.
Results on the fifth day of the Shanghai Masters on Thursday (x denotes seeding):
Tomas Berdych (CZE x4) bt Sam Querrey (USA) 6-2, 6-7 (3/7), 6-4
Jo-Wilfried Tsonga (FRA x5) bt Marcos Baghdatis (CYP) 6-2, 7-6 (7/2)
Novak Djokovic (SRB x2) bt Feliciano Lopez (ESP) 6-3, 6-3
Andy Murray (GBR x3) bt Alexandr Dolgopolov (UKR) 6-2, 6-2
Radek Stepanek (CZE) bt John Isner (USA x8) 6-4, 6-7 (5/7), 6-3
Marin Cilic (CRO x10) bt Fernando Verdasco (ESP) 4-6, 6-1, 6-4
Roger Federer (SUI x1) bt Stanislas Wawrinka (SUI x13) 4-6, 7-6 (7/4), 6-0
Tommy Haas (GER) bt Janko Tipsarevic (SRB) 6-2, 6-1