Japan's Naomi Osaka admitted she has "never been so nervous" after coming within just two points of a sensational first round Roland Garros exit on Tuesday.
The world number one battled back from a set and a break down to defeat Slovakia's Anna Karolina Schmiedlova 0-6, 7-6 (7/4), 6-1 to extend her winning streak at the Slams to 15 matches.
However, Osaka, bidding to add the French Open to her US and Australian Open titles, was close to becoming just the second top seed to lose in the first round in Paris in the modern era after Angelique Kerber in 2017.
World number 90 Schmiedlova, who hadn't won a match at the tournament since 2014, twice served for the tie in the 10th and 12th games of the second set.
At one stage, she was just two points away from a famous victory.
But Osaka, who had arrived in Paris still feeling the effects of a hand injury suffered in Rome, battled back to set-up a second round duel with former world number one and two-time major winner Victoria Azarenka.
"I think this is the most nervous I have ever been my entire life during a match," said Osaka.
"I think you could see that in the first set. I was literally not hitting any balls in the court.
"For me, today was weird because usually the nerves go away, but it kind of stayed the entire match. Then I just felt like it was a fight of willpower."
Osaka said she had only practiced on the cavernous Court Philippe Chatrier for 30 minutes since her arrival in the French capital.
She was also totting up the reasons why she was so under-powered.
"First time playing a Grand Slam as No. 1. I have won the last two, so I kind of want to win this one really bad.
"Also I have never played on Chatrier before. This was my first time. And, yeah, I kind of feel like I'm having the thought of wanting to prove myself again, so..."
Osaka was broken three times in the opening set, losing it in just 20 minutes.
The 21-year-old hit 13 unforced errors while the Slovakian didn't need to hit a single winner such was the error-strewn show coming from the other side of the net.
The Japanese star had not been 'bageled' since the Wimbledon second round in 2017.
Osaka recovered her composure for a break and a 3-0 lead in the second set but a brief suspension for rain disrupted her composure and allowed the Slovakian to hit back to 3-3.
Former top 30 player Schmiedlova served for the tie at 5-4 but Osaka dug deep to save herself.
The errors kept coming and the 24-year-old Slovakian was handed a second chance to serve for victory.
Still, she couldn't convert despite being just two points from victory and Osaka stayed alive, sweeping through the tie-breaker.
That was the cue for Osaka to illustrate the gap of 89 places between her and the slender blonde in the world rankings.
She broke three times in a quickfire 25-minute final set to extend her streak at the Slams to 15 successive wins.
Osaka ended the match with 10 aces, 36 winners and 38 unforced errors with just four of those coming in the decider.
"I was really close, so it hurts I lost so many chances," said Schmiedlova.
"Maybe I felt like it was against the world number one. It was not easy in my head."
Azarenka, a semi-finalist in 2013, reached the second round for the first time since 2015 with a 6-4, 7-6 (7/4) win over 2017 champion Jelena Ostapenko.
Azarenka stands at 1-1 in head to heads with Osaka.
She won their first meeting at the 2016 Australian Open before Osaka gained revenge on clay in Rome last year.