Roger Federer's next opponent at Wimbledon is the last man to win the title before the Swiss star began his run of five straight championships. And beyond that could be a matchup with the last player to beat him at Wimbledon six years ago.

After a relatively easy stroll through the first three rounds, things could start to get trickier for Federer as he continues his march toward a sixth championship at the All England Club.

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Next up in the round of 16 on Monday will be Lleyton Hewitt, the scrappy Australian who won the title in 2002.

"With him being a former No. 1, former champion here, I think it's an intriguing match for both of us," Federer said.

The two have met 20 times — with Federer winning the last 11 dating back to the 2004 Australian Open and holding an overall edge of 13-7. In their only two previous Wimbledon matchups, Federer won in the 2004 quarterfinals and 2005 semifinals.

"I've definitely played well against him the last times I've played him," Federer said after sweeping past Marc Gicquel 6-3, 6-3, 6-1 on Friday. "It's always a challenge playing Lleyton. He's a great player, a guy I really enjoy watching. He's a great competitor. He knows what it takes to win slams."

Their rivalry goes back to the juniors when they first played against each other at age 15. Federer recalls winning after saving a match point.

Hewitt, who has been slowed by a chronic hip injury and slipped to a world ranking of No. 27, said serving and returning will be the key against Federer.

"Against a guy like Roger, you really have to take those half chances when you get them because you're not going to get a lot of them," he said.

Hewitt dismissed the notion that Federer was more vulnerable this year following his semifinal loss to Novak Djokovic at the Australian Open and lopsided defeat to Rafael Nadal in the French Open final.

"Not really," Hewitt said. "I think he feels very comfortable. He's played all his matches on Centre Court so far again this year. He feels right at home on that stage. I think he's going to still have that aura and that self-confidence behind him."

Federer does seem back in his element. Friday's victory extended his winning streak at Wimbledon to 37 matches and 62 overall on grass.

"Playing at Wimbledon always creates extra pressure because it's what's closest to my heart," he said. "Maybe (I) wish someday my career ends here in a way because it's the most prestigious tournament we have on tour. That alone create pressure, so I want to prove it to myself I can do it again here."

If Federer gets past Hewitt, he could face a dangerous floater in the quarters. Mario Ancic was the last player to have beaten Federer at Wimbledon — he did so as a qualifier in the first round in 2002.

The Croatian outlasted fifth-seeded David Ferrer 6-4, 6-4, 6-7 (5), 7-6 (3) on Friday in a match that ended on Centre Court in near darkness around 9:15 p.m.

"I'm so happy I'm back again," said the 6-foot-5 Ancic, who missed last year's Wimbledon with glandular fever. "This is a big moment for me, playing on this ground. So many great matches, great memories. I was looking forward to playing on Centre Court."

To earn a possible Centre Court matchup with Federer next week, Ancic will need to beat Fernando Verdasco in the fourth round.

The tournament has been jolted by a series of early-round upsets that have decimated the seeding lists.

Six of the top-10 seeded men have been knocked out so far before the fourth round: No. 3 Djokovic, No. 4 Nikolay Davydenko, No. 5 Ferrer, No. 6 Andy Roddick, No. 7 David Nalbandian and No. 9 James Blake.

No. 1 Ana Ivanovic's loss Friday to 133rd-ranked Zheng Jie of China means two of the top three seeded women are already gone. No. 3 Maria Sharapova, the 2004 champion, was bounced out Thursday by 154th-ranked Alla Kudryavtseva.

Ivanovic, who took over the No. 1 ranking after winning the French Open earlier this month, didn't play any grass-court warmup tournaments and never found her game.

She saved two match points before overcoming Nathalie Dechy in three sets on Wednesday, but got no reprieve this time and slumped to a 6-1, 6-4 loss to Zheng, a wild-card entry whose greatest success has been in doubles.

"It was a very emotional last couple of weeks for me and it took a bit of a toll," Ivanovic said. "I didn't have great preparation."

Ivanovic could now lose the No. 1 ranking depending on how far Jankovic and No. 4 Svetlana Kuznetsova advance in the tournament.

Avoiding the upset trend so far has been No. 2 Jelena Jankovic, who was set to lead off play on Centre Court on Saturday against Caroline Wozniacki. Defending champion and four-time winner Venus Williams was scheduled on Court 1 against Maria Jose Martinez Sanchez.

Nadal, who lost to Federer in the last two finals, was paired against Nicolas Kiefer.

Not a single American is left in the men's singles draw. Only one, Bobby Reynolds, made it to the third round, the worst showing since 1926. And he lost Friday to Feliciano Lopez of Spain 6-4, 7-5, 4-6, 6-4.

"Obviously it's discouraging," Reynolds said. "I was the last one and it's only the third round. That's not something we like to tip our hats to."