Federer, Soderling to meet

WIMBLEDON, England -- When Roger Federer misfired on an important shot Friday, his knees buckled and he stomped behind the baseline, miffed at his mere mortality.

The moment quickly passed, and Federer advanced to the second week at Wimbledon by defeating Philipp Kohlschreiber 6-3, 6-2, 6-7 (5), 6-1.

Novak Djokovic, who could face Federer in the semifinals, also reached the fourth round with a 6-4, 6-4, 6-4 win over American Mardy Fish.

Federer lost a set for first time this week, with two errant forehands costing him the tiebreak. That extended his Centre Court workout by only half an hour.

"It has been a good first week," he said. "Pretty convincing. I thought this was my best match of the tournament, even though I dropped a set. I'm excited about the second week."

Federer earned a berth in the fourth round Monday against a familiar foe -- Robin Soderling. Federer defeated Soderling in the French Open final this month to complete a career Grand Slam and win his 14th major title, tying Pete Sampras' record.

"It's tough to play against Roger. I've played him 10 times, and after the match I never felt like I played well. But, I mean, it's not because of me -- I think it's because of him. He makes you play," said Soderling, 0-10 against Federer. "It's tough to play well against him, put it that way."

Now the No. 2-seeded Federer seeks his sixth Wimbledon title, and he's a heavy favorite with defending champion Rafael Nadal absent because of bad knees.

"It's down to business in the second week," Federer said. "This is where it gets really interesting."

Federer played on Centre Court, where the new retractable roof was open for the fifth consecutive day.

Federer could have won more quickly. He converted only seven of 22 break-point chances and led 4-2 in the third set before the No. 32-ranked Kohlschreiber played his best stretch of tennis.

Federer's rare display of frustration came after he pulled an easy forehand wide trailing 5-4 in the tiebreak. Two points later, Kohlschreiber ripped a backhand winner to force a fourth set, but Federer pulled away from there and extended his winning streak to 15 matches, his longest in two years.

"Sure, I would have loved to win in straight sets, but he came back strong," Federer said. "I was happy how I reacted. I didn't panic."

Soderling reached the fourth round for the first time by defeating Nicolas Almagro 7-6 (7), 6-4, 6-4. Soderling lost only three points on his first serve and never faced a break point.

Djokovic, who made a shocking exit in the second round last year, converted his first match point with a service winner. The 22-year-old Djokovic broke Fish four times and lost serve only once.

Fish reached the third round at Wimbledon for the third time but has never advanced to the round of 16.

Djokovic, largely ignored so far amid all the hype over a possible Federer-Andy Murray final, fired an unreturnable serve to win the match then threw his wristbands into the crowd.

"It was a very solid performance and I played really good tennis and it's encouraging that I was winning a lot of service games quite easily," the Serbian fourth seed said after extending his record over Fish to 4-0.

"I was always dreaming of winning Wimbledon, it's the most prestigious event so hopefully I will have the opportunity and honor one day," he said.

Being under the radar suited Djokovic.

"Right now, I feel quite OK that people are not talking about me too often, which gives me a freedom to perform the best tennis I can on the court," he said. "Andy is from this country and obviously a lot of people expect him to do well and to become the first British player to win Wimbledon after a long time.

"Then, on the other hand, you have Roger, who has equaled the record of Sampras' Grand Slam victories and [has] five Wimbledons under his belt, so he's very respected here. It's normal that they are in the spotlight in this moment," he said.

The 2008 Australian Open champion next faces Dudi Sela, who became the first Israeli man in 20 years to reach the fourth round at Wimbledon. Sela threw his racket in anger after going down a break in the fourth set but rallied to beat Tommy Robredo of Spain 7-6 (8), 7-5, 2-6, 7-5.

Sela became just the fourth Israeli man to reach the round of 16 in a Grand Slam tournament and the first since Amos Mansdorf at the 1992 Australian Open. Mansdorf also accomplished the feat at Wimbledon in 1989.

"In Israel, we have only hard courts, so I was expecting more to do better ... on the hard courts than on grass or clay," Sela said. "But any Grand Slam fourth round, it's good, I think."

Ivo Karlovic of Croatia hit 46 aces in a close third-round upset of No. 9-seeded Jo-Wilfried Tsonga.

The 22nd-seeded Karlovic never faced a break point and ended his 7-6 (5), 6-7 (5), 7-5, 7-6 (5) victory over the 2008 Australian Open runner-up with an ace.

"What I can say?" said Tsonga. "He served well, and that's it."

Karlovic will play seventh-seeded Fernando Verdasco of Spain, a 4-6, 6-1, 6-4, 7-6 (2) winner over fellow Spaniard Albert Montanes, in the fourth round.

Karlovic, the tour leader in aces in 2009, hit a modern era-record 55 in a loss at the French Open last month.

Told about Karlovic's 46 aces, Federer was not particularly surprised -- or impressed.

"No disrespect to Karlovic, but that is not really a tennis match. Just a stroke of luck or bad calls at the bad time -- and what can you do? I lost to him too last year," said Federer, who could meet Karlovic in the quarterfinals. "Once you get to the tiebreaker, he knows it and we know it: It is 50-50.

"I think he is a good draw for players who are less highly ranked, and he is a bad draw for those who are stronger, because I have the impression that he manages to up the level of his serve against us," Federer said.

Does Karlovic mind when people criticize him for having a tremendous serve and little else to his game?

"Actually, I mean, I like it," the Croatian said with a smile, "because if I can win with only one shot, I'm, I don't know, a genius."

Karlovic is best known for stunning 2002 champion Lleyton Hewitt in Wimbledon's first round the following year. Karlovic lost his opening matches at the All England Club from 2005 to '08.

Two marathon matches were suspended because of darkness, with No. 11 Marin Cilic and No. 24 Tommy Haas at 6-all in the fifth set and No. 29 Igor Andreev leading Andreas Seppi 6-1, 7-6 (5), 4-6, 5-5. Those are scheduled to resume Saturday.

Information from The Associated Press and Reuters was used in this report.