Stuck in what she later would call a "really big hole" in the third set against a much younger opponent, the seven-time Grand Slam champion tried to put aside the weak serving and errant shots that created the mess in the first place.
In the end, it was too much to overcome.
Wincing after some points, resting with hands on knees after others, the 30th-seeded Williams lost 7-6 (5), 6-7 (4), 6-4 Sunday to 40th-ranked Urszula Radwanska of Poland. Williams last exited Roland Garros in the first round 12 years ago.
After the 3-hour, 19-minute match, filled with ebbs and flows, a reporter asked whether it crossed the 32-year-old Williams' mind that this might have been the last French Open of her career.
"If it's the last match, I'll let you know," she answered. "That's pretty much how it works."
Still adjusting to living with an energy-sapping autoimmune disease she revealed in August 2011, Williams now has two first-round losses in the past four Grand Slam tournaments. Her defeat at Wimbledon last June was the first time she'd left a major championship that early since she lost in the first round of the Australian Open 6 1/2 years earlier.
"With what I've gone through, it's not easy. But I'm strong and I'm a fighter. You know, I don't think I'm just playing for me now. I think I'm playing for a lot of people who haven't felt well," the American said. "I think for me today it's a positive to be able to play three hours."
Inflammation in her lower back limited Williams to two matches over the previous 1 1/2 months, preparation she called, with a chuckle, "extremely un-ideal."
"I can't really serve very hard. It's painful when I do that. But I'm getting better. I just, you know, ran out of time to get better for this tournament," said Williams, who was broken 11 of the 17 times she served Sunday. "My strategy was more or less to put the ball in, and that's very difficult for me, too, because that's not who I am. But that's all I had."
This result came a year after she lost in the second round at Roland Garros to Radwanska's older sister, Agnieszka, the 2012 Wimbledon runner-up.
Agnieszka is seeded fourth at the French Open and will play her first-round match Monday against Shahar Peer of Israel. Others in action on Day 2 include seven-time champion Rafael Nadal, and the past two winners of the women's title, Maria Sharapova and Li Na.
"Yeah, of course, I was talking with Aga about Venus," Urszula said. "I was well-prepared for this match, and I knew she was a great fighter, so I should be focused the whole match."
Williams, naturally, also knows a thing or two about having a more successful tennis-playing sibling, and her short stay in Paris comes 12 months after younger sister Serena, who owns 15 Grand Slam titles, was upset in the first round at Roland Garros.
Serena made a fluent return to the clay-court tournament in the early afternoon Sunday, overwhelming 74th-ranked Anna Tatishvili 6-0, 6-1 — and then addressing an appreciative audience at Court Philippe Chatrier in the local language.
"I have been speaking French for years and years, but I don't really have a lot of confidence," Serena said later, in English. "It's way, way more nerve-racking than playing tennis."
On this day, for her, absolutely.
She won the first nine games against Tatishvili, and 30 of the first 37 points. On her serve, the final count was 28 of 33 points, bolstered by eight aces.
"I've played a lot of players who have very good serves, but hers is consistently good, so you always feel pressure when you're returning," Tatishvili said. "I wasn't really surprised, because I've watched her so much, you know? It's Serena Williams; you watch her always on TV or at tournaments. But it's the first time I felt what I had seen."
Serena actually had hoped to show off her French skills last year, but never got the chance to deliver remarks after a victory. That's because she lost her opening match to Virginie Razzano — her only first-round defeat in 51 career Grand Slam tournaments.
Venus was one of two seeded players knocked out Sunday: No. 11 Nadia Petrova of Russia was beaten by Monica Puig of Puerto Rico 3-6, 7-5, 6-4. Otherwise, results went to form, with 17-time major champion Roger Federer picking up a 6-2, 6-2, 6-3 victory over a guy making his Grand Slam debut, Pablo Carreno Busta of Spain, while No. 4 David Ferrer, No. 14 Milos Raonic of Canada and No. 18 Sam Querrey of the United Sates also were among the winners.
Ana Ivanovic, the 2008 champion, and Sara Errani, the 2012 runner-up, advanced in straight sets in the women's draw.
The Williams sisters helped change the way women's tennis was played in the late 1990s and early 2000s, with 120 mph serves, stinging forehands and fantastic court coverage. They faced each other in eight Grand Slam finals, including the 2002 French Open, which Serena won.
Neither Williams has enjoyed much success in Paris after that championship match, where the clay tends to dull the strength of their swings and the footing can give them problems. Venus hasn't been past the quarterfinals since 2002, while Serena hasn't since 2003.
"I just keep trying, and it hasn't been working out for me," Serena, who is ranked and seeded No. 1, said after stretching her career-best winning streak to 25 matches. "I may have gotten nervous in the past or may have basically choked a few matches away."
Venus nearly fashioned a turnaround after being three points from defeat while trailing 4-0 in the second-set tiebreaker. She won the next seven points in a row, though, to force a third set. Then she promptly fell behind 4-0, and 5-1, before making things interesting by taking three straight games as a handful of spectators in nearly empty Court Suzanne Lenglen clapped and chanted, "Let's go, Venus, let's go!"
But it ended with one last miscue by Venus, her 66th unforced error, a backhand dumped into the net.
"I'm just trying to handle defeats better, because it's no fun having a bad attitude about it. So I try to move on," Venus said. "It helps if you had some wins in the past, too. Those keep you warm at night. I have a lot of wins under my belt that help me feel better."
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