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 beating Philipp Kohlschreiber 6-3, 6-2, 6-7 (5), 6-1.
Federer lost a set for the first time this week, with two errant forehands costing him the tiebreaker. That merely extended his Centre Court workout by 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."
Federer earned a berth in the fourth round Monday against a familiar foe -- Robin Soderling. Federer beat Soderling in the French Open final this month to complete a career Grand Slam and win his 14th major title, tying Pete Sampras' record.
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."
While Federer played on Centre Court, where the new retractable roof remained open for the fifth consecutive day, two-time champion Serena Williams was assigned to Court 2 and arrived six minutes late for her match. Otherwise Williams remained right on schedule, beating Roberta Vinci 6-3, 6-4.
Fourth-seeded Novak Djokovic, who could face Federer in the semifinals, defeated American Mardy Fish 6-4, 6-4, 6-4.
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 tiebreaker.
Two points later, Kohlschreiber ripped a backhand winner to force a fourth set, but Federer pulled away 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 in seven appearances at Wimbledon by defeating Nicolas Almagro 7-6 (7), 6-4, 6-4. The Swede lost only three points on his first serve and never faced a break point.
Up next: Federer. Soderling has lost all 10 of their matches.
"It's tough to play against Roger," Soderling said. "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."
Unseeded Dudi Sela became the first Israeli man in 20 years to reach the fourth round when he beat No. 15 Tommy Robredo 7-6 (8), 7-5, 2-6, 7-5. The 22nd-seeded Ivo Karlovic hit 46 aces, the last on match point, to upset No. 9 Jo-Wilfried Tsonga 7-6 (5), 6-7 (5), 7-5, 7-6 (5).
In women's play, 19-year-old Victoria Azarenka made a successful Centre Court debut by beating Sorana Cirstea 7-6 (2), 6-3. Gisela Dulko, who upset 2004 champion Maria Sharapova in the second round, was eliminated by No. 10 Nadia Petrova 3-6, 6-3, 6-4.
Seventh-seeded Vera Zvonareva, slowed by an ankle injury since April, pulled out before her match against No. 26 Virginie Razzano. Fourth-seeded Elena Dementieva, a semifinalist last year, cruised past qualifier Regina Kulikova 6-1, 6-2.