WIMBLEDON, England — When 17-year-old American Melanie Oudin concluded the biggest match of her life Saturday at Wimbledon, she had trouble finding the exit on cozy Court 3.

Still learning her way around the All England Club, Oudin has made it into the fourth round. The qualifier from Marietta, Ga., pulled off the upset of the week by beating former No. 1 Jelena Jankovic, 6-7 (8), 7-5, 6-2.

‘‘I was just thinking that she was any other player,’’ Oudin said, ‘‘and this was any other match, and I was at any other tournament — not like on the biggest stage at Wimbledon. I think I handled it really well.’’

The sixth-seeded Jankovic struggled with the heat on a sunny, 82-degree afternoon, and took a 12-minute break after the first set. She was plagued by erratic groundstrokes, while Oudin played with poise down the stretch and swept the final three games.

Oudin gives downtrodden U.S. tennis a boost by joining the Williams sisters in the round of 16.

‘‘Super good news,’’ said Venus Williams, who played at the same time as Oudin and beat Carla Suarez Navarro 6-0, 6-4.

Oudin’s so young her earliest Wimbledon memory is watching the Williams sisters on TV.

‘‘When I was like 7, when I started playing tennis, I saw Venus and Serena Williams playing here and I was like, ’Mom, I really, really want to play there one day,’’’ Oudin said. ‘‘She said, ’Go for it.’ My parents have always been very supportive.’’

One U.S. player reached the men’s round of 16 — two-time runner-up Andy Roddick. He hit the last of his 33 aces on match point to beat friend Jurgen Melzer 7-6 (2), 7-6 (2), 4-6, 6-3.

The No. 6-seeded Roddick is 22-3 in tiebreakers this year, and he improved to 9-0 against Melzer. Roddick’s opponent Monday will be No. 20 Tomas Berdych, who eliminated No. 12 Nikolay Davydenko 6-2, 6-3, 6-2.

American Jesse Levine’s best run at a major event came to an end. The last qualifier in the men’s draw, Levine faced 23 break points and lost to No. 19 Stanislas Wawrinka 5-7, 7-5, 6-3, 6-3.

Wawrinka will next play No. 3 Andy Murray, seeking to become the first British man to win Wimbledon since 1936.

He defeated No. 30 Viktor Troicki 6-2, 6-3, 6-4.

Unseeded Lleyton Hewitt, the 2002 champion, reached the fourth round for the sixth year in a row by beating Philipp Petzschner 7-5, 7-6 (3), 6-3.

A few drops of rain fell late in the session, but there was no halt in play, and the new retractable roof on Centre Court wasn’t needed for a sixth consecutive day.

Oudin wasn’t the only teen to make a splash on the final day of the first week. Unseeded 19-year-old Sabine Lisicki of Germany upset No. 5 Svetlana Kuznetsova, the French Open champion, 6-2, 7-5.

‘‘Before I came into this Wimbledon championships, I hadn’t won, actually, a match on grass,’’ Lisicki said. ‘‘I just can’t believe I’m in the fourth round.’’

No. 9-seeded Caroline Wozniacki, 18, also advanced. Top-ranked Dinara Safina, enjoying her best Wimbledon, beat Kirsten Flipkens 7-5, 6-1.

Oudin (pronounced oo-DAN) arrived in London with an 0-2 record in Grand Slam matches, and she had to win three qualifying matches to make Wimbledon’s main draw for the first time. She’s ranked 124th and will crack the top 100 for the first time after the tournament.

Facing a top-10 opponent for the first time, Oudin wore down Jankovic in an arduous first set. The teenager failed to convert four set points, committing an unforced error each time. But when the 66-minute set ended, it was Jankovic who appeared on the ropes.

A trainer and doctor came on court to check Jankovic’s pulse and blood pressure. She rested on a towel while being treated, and after several minutes sat up while ice was applied to her neck and midsection.

Jankovic later said she was ailing in part because of ‘‘woman problems.’’

‘‘It’s not easy being a woman, you know, sometimes,’’ Jankovic said. ‘‘After the first set, I felt really dizzy, and I thought that I was just going to end up in the hospital. I started to shake. I was losing my, how you say, consciousness. …

‘‘I came back, like I started to feel a little bit better. But I was feeling quite weak. No power. I wasn’t the same player.’’

Jankovic played on, but the Serb has struggled all year to regain the form that made her the U.S. Open runner-up in 2008.

The match turned when Oudin overcame a 5-4 deficit in the second set. She repeatedly won points with drop shots, punctuating winners with shouts of ‘‘Come on!’’ The teenager smacked a forehand winner on the final point, then raised her arms with glee.

‘‘I go into every match the exact same, you know, like no matter who I play,’’ Oudin said. ‘‘It’s not like, ’Oh my gosh, I’m playing the No. 1 player in the world.’ Every match is the same for me, because it all depends on what game I play and what shots I hit and all that stuff.’’

Five-time champion Williams took charge early against the 34th-ranked Suarez Navarro, winning the first eight games. Williams, playing with a strap on her left leg for the second match in a row, avenged a loss to Suarez Navarro in the second round at the Australian Open in January.

Bidding for her third consecutive Wimbledon title, the No. 3-seeded Williams next will play 2008 French Open champion Ana Ivanovic, who beat 2009 Roland Garros semifinalist Samantha Stosur 7-5, 6-2.