PARIS -- Venus Williams bounced back from a poor start at the French Open on Sunday, beating 19-year-old Paula Ormaechea 4-6, 6-1, 6-3 in her first Grand Slam match since revealing she has been diagnosed with an autoimmune disease.
The seven-time major champion seemed taken aback by her opponent's early aggressive play, but still managed to turn the match her way and reach the second round.
The 31-year-old Williams, a former top-ranked player who is now No. 53, is 12-4 this season.
Williams pulled out of the U.S. Open last August before her second-round match, saying she had Sjogren's syndrome, an autoimmune disease that can cause fatigue and joint pain. She returned to the tour in March.
"A lot of it, I have to figure it out. It's physical and emotional and all kinds of different things. Mental," Williams said of her medical condition. "It's a big accomplishment for me to be here right now."
She looked glum on court, not even smiling after most of her 41 winners (Ormaechea only had 15). But she laughed frequently during her news conference, such as when she talked about what she's been going through as "definitely an adventure and journey; it's life happening."
Oudin, a 20-year-old from Marietta, Ga., is ranked 269th but got into the main draw at Roland Garros thanks to a wild card handed out by the U.S. Tennis Association based on results at low-level clay-court tournaments in the United States.
"I was putting so much pressure on myself," said Oudin, who will face No. 21-seeded Sara Errani of Italy in the second round. "Now I feel like I am the underdog."
Oudin -- whose name is pronounced "oo-DAN," because of her French heritage, yet was repeatedly mispronounced by the chair umpire as "oo-DEEN" -- double-faulted on the first point and trailed 2-0.
"I was a little bit nervous. I could tell. I mean, my feet weren't really moving in the beginning. I definitely needed to just loosen up a little bit," Oudin said.
She did, winning 10 of the next 12 games, including 10 consecutive points in one stretch, often yelling "Come on!" after one of her 23 winners or Larsson's 28 unforced errors.
"That's the biggest thing when I'm out there: I believe I can win these matches again," said Oudin, who entered the day 0-2 at the French Open and without a victory in a completed main-draw match at any tour-level event in more than a year.
At age 17, an unseeded and unknown Oudin -- with the word "Believe" printed on the sides of her shoes -- knocked off four Russians, including three-time major champion Maria Sharapova and 2008 Beijing Olympic champion Elena Dementieva, during a captivating run at the U.S. Open.
Oudin became the tournament's youngest quarterfinalist since Serena Williams in 1999.
No one counted on her winning as many matches as she did: Her hotel reservation in New York didn't cover enough nights, so she wound up having to change places. It was heady stuff, including a new endorsement Oudin signed about 20 minutes before heading out for what turned out to be her last match at that U.S. Open.
From there, expectations weighed Oudin down, and losses piled up. Clearly, it was time to change something, so she started by splitting with coach Brian de Villiers last October.
"Not easy, for sure," she said. "I was with him forever, ever since I was a little kid."
It all began to turn around when Oudin won two matches in qualifying rounds to get into April's WTA tournament at Charleston, S.C. Before that, she was 0-5 in 2012, including at lower-tier events.
"The hardest part was winning the first match," Oudin said. "Ever since then, I've been playing pretty well. I mean, I haven't been getting tight at all in matches. I haven't been playing with any pressure. I've really been playing to win and playing with much more confidence."
Larsson said she handed Oudin "a present" by playing poorly, something the Swede attributed to an abdominal muscle injury that bothered her most while serving. In the second set, Larsson double-faulted once when her second serve went off her frame and nearly hit the chair umpire.
"I could not play as good as I can," Larsson said. "It was frustrating to see her get so happy after the match."
Ivanovic beat Lara Arruabarrena-Vecino of Spain 6-1, 6-1.
Ivanovic won her only major title at Roland Garros in 2008, but lost in the fourth round a year later. She fell in the second round in 2010, and then lost in the first round last year.
Kuznetsova, the former top-ranked Serb had five aces and 27 winners against Arruabarrena-Vecino, who finished the match with only four winners.
The sixth-seeded Stosur, who won last year's U.S. Open title and reached the final at Roland Garros in 2010, beat Elena Baltacha of Britain 6-4, 6-0.
"It's a bit of an early start, but always nice to get through it now," the Australian said. "You have the whole day and whatever else to recover and, yeah, enjoy."
Kuznetsova won the French Open title in 2009 and U.S. Open in 2004 but is seeded No. 26 this year. Against Mirjana Lucic of Croatia, the Russian faced little trouble despite being broken once in the second set.
The French Open is the only Grand Slam tournament that starts on Sunday. The other three all start on Monday.
"I don't think it's too big a deal now that it's more of a proper schedule," Stosur said. "I think the first year there was only a handful of matches, and, yeah, if you were on the schedule then, it really didn't feel like the tournament started. Nobody else was thinking that the tournament had started."
Stosur converted five of her eight break points, and only briefly allowed Baltacha back into the match by being broken while serving for the first set at 5-3. The Australian broke right back to take the set.
In the second set, Baltacha won only four points on her serve, allowing Stosur to advance easily.
Kuznetsova raced through the first set of her match, and then held on to win the second to reach the next round. After leading 3-0 in the second set, Lucic broke twice to get back to 3-3, but Kuznetsova then won the next three games to take the match.
The 30-year-old Lucic reached the Wimbledon semifinals in 1999, but she is now 11-44 against players ranked in the top 30 in her career.
Information from The Associated Press was used in this report.