Fourth seed Alexander Zverev was teetering on the brink of defeat when he trailed Taylor Fritz of the United States by two sets to one when their second round tie was suspended for the night.
The Romanian world number one takes on Hsieh Su-wei from Taiwan next.
This year's early loss was surprising because the Spaniard seemed to be poised for a deep run after a strong French Open, where she trounced Maria Sharapova in the quarter-finals before losing to eventual champion Simona Halep in the semi-finals.
Third seed Marin Cilic was stunned 3-6 1-6 6-4 7-6 (3) 7-5 by Argentina's world number 82 Guido Pella in three hours 12 minutes. The Romanian won the last 10 games of her match with Zheng Saisai to advance 7-5 6-3 while qualifier Eugenie Bouchard will leave Wimbledon with momentum despite a 6-4 7-5 loss to Ash Barty in a battle of former Wimbledon junior champions.
"I wasn't thinking I had to defend anything, I was just thinking of trying to win". At No. 237, Liu was the lowest-ranked woman to make the second round.
Belgian 47th-ranked Van Uytvanck triumphed 5-7, 6-2, 6-1 for her first-ever win over a top 10 opponent.
No. 7 Karolina Pliskova is the other top-eight-seeded woman left in the draw. You always want that first game, you know. "If schedule is out they can not change it but anyway I would like to talk to them about why they did it because I think now we are not in rush, but I will try to do my best to be ready and show my best", said the 22-year-old Siniakova.
"I think we both played pretty well and it was a pretty close match".
When Garbine Muguruza clutched her temple with both hands and shook her head repeatedly, she laid bare the throbbing pain racing through her body as her Wimbledon title defence was hijacked by a little-known Belgian on Thursday.
"I feel good on grass now", said Halep, who after the first set overcame the hard Zheng slice.
Muguruza, meanwhile, not only won her second career Grand Slam title in 2017 at Wimbledon, but also reached the 2015 final.
Three of the next four games would be breaks, including Muguruza failing to serve out the set at 5-4.
Wimbledon giant-killer Alison van Uytvanck said Thursday, July 5, she was comfortable coming out as gay, saying "it is not a disease".
A good hold for van Uytvanck had her leading the way to start the match hoping to keep her pace together against what Muguruza produced. I am a little bit surprised they put me first match so I think I will ask why.
"I would love to be in the second week for the first time for me in Wimbledon", she added.