Federer strolls, Djokovic, Murray scramble

Roger Federer moved into the Olympic quarter-finals with minimum fuss on Wednesday, while his gold medal rivals Novak Djokovic and Andy Murray had to dig deep to avoid third round exits.

After securing a record-equalling seventh Wimbledon title, Federer is desperate to complete a career 'Golden Slam' by winning singles gold for the first time.

The 17-time grand slam singles champion saw the defence of his doubles title with Stanislas Wawrinka fall apart with a 1-6, 7-6 (7/5), 6-3 loss to Israel's Jonathan Erlich and Andy Ram.

But Federer stayed on course for the singles with a 7-5, 6-3 win over Uzbekistan's Denis Istomin on Wimbledon's Court One.

Federer, 30, will play John Isner for a place in the semi-finals after the American 10th seed defeated Serbian seventh seed Janko Tipsarevic 7-5, 7-6 (16-14).

"I started really well and went into the lead 3-0. But he came back and I was a little bit shaken up I guess," Federer said.

"I got a bit lucky obviously, saving a couple of set points. Then I think I was able to play a bit more aggressively, I relaxed and I played a good match in the end."

World number two Djokovic, scheduled to face Federer in the Olympic final, endured a much tougher test as he came from behind to beat Australian veteran Lleyton Hewitt 4-6, 7-5, 6-1.

Djokovic was pushed to the brink in a gruelling clash on Centre Court before finally overpowering the gritty Hewitt in one hour and 56 minutes.

Next up for the 2011 Wimbledon champion is French fifth seed Jo-Wilfried Tsonga, who beat Spain's Feliciano Lopez 7-6 (7/5), 6-4.

"It was great, it was a really good test for both of us," Djokovic said.

"I thought he was the better player for half of the match. He was returning exceptionally well and serving quite precisely.

"I was in trouble, especially in the second set when I didn't serve out the set at 5-3. But I managed to compose myself and play my best when I needed to."

Britain's Andy Murray also survived a stern examination from Cyprus's Marcos Baghdatis before coming through 4-6, 6-1, 6-4.

Murray had started his bid for Olympic gold in superb form, but Baghdatis pushed him hard in the Wimbledon third round last month and the world number 44 proved a tough opponent again at the same stage of the Games.

In windy conditions on Centre Court, Murray looked in danger of a shock defeat as the world number four was out-played in the first set.

But the Scot, beaten in this year's Wimbledon final by Federer, finally found enough momentum to edge through to a last-eight clash with Spanish 11th seed Nicolas Almagro, who defeated Belgium's Steve Darcis 7-5, 6-3.

"I was struggling in the first set. Guys like Marcos, he's ranked 40 or 50 in the world, but when he plays his best tennis, he's so, so tough to beat," Murray said.

"That's why you can't really afford slow starts. I was lucky to get away with it today."

Former US Open champion Juan Martin del Potro, seeded eighth, also advanced to the quarter-finals, beating French 12th seed Gilles Simon 6-1, 4-6, 6-3.

Argentina's del Potro will play Japan's Kei Nishikori, who shocked Spanish fourth seed David Ferrer 6-0, 3-6, 6-4 in a match which finished under the floodlit Centre Court roof after starting outdoors on Court 14.