The Belarusian lost the top spot in the world rankings to Kazakhstan's Elena Rybakina last month, and has not won any title since last March, in a period witnessing a notable decline in her results.
Sabalenka, who played the match with a medical protective tape around her right knee, appeared to be on her way to clinching the match, before her American opponent succeeded in turning the tide of the match midway through the second set, taking advantage of the Belarusian's declining performance.
At the start of the deciding set, Sabalenka requested medical intervention after losing her serve, in a scene that reflected her clear struggle with movement. Despite this, the former world number one showed great fighting spirit, coming back from a 2-5 deficit and saving nine match points, keeping her hopes alive until the final moments.
However, Li maintained her composure in the final stages and succeeded in capitalizing on her tenth opportunity to clinch the match after two hours and 27 minutes of competition, booking her seat in the round of 16 where she will face Indonesia's Janice Tjen.
Sabalenka was not the only star to leave the tournament early, as she was joined by American Jessica Pegula, the second seed and runner-up of last year's edition, after she fell in turn to Latvian Jelena Ostapenko 2-6, 7-6 (7/9), and 6-3, in another surprise that saw Pegula waste three match points.
Ostapenko achieved a remarkable feat, becoming the first player to manage to eliminate Pegula from her opening match in a 1000-point tournament since the Indian Wells tournament two and a half years ago, putting an end to the American's winning streak in 22 consecutive opening matches in this category of tournaments.
Swiatek qualifies easily
In turn, Poland's Iga Swiatek, ranked ninth in the world, began her journey with a crushing 6-2, 6-1 victory over Magdalena Frech, in an all-Polish confrontation in the second round.
This is the 40th win this year for the winner of six Grand Slam titles.
Swiatek, the seventh seed in the tournament who needed one hour and 42 minutes to defeat her compatriot who qualified for this round as a "lucky loser," said: "We know each other well, so I wanted to focus on consistency and perform as well as possible."
The Pole, who is seeking to qualify for the season-ending WTA Finals scheduled in Indian Wells between November 8 and 15, added: "I know she always runs for every ball, and sometimes she uses her opponent's power, so I wanted to play with consistency and balance, and I am happy that I did that."
Despite the crushing result, the first set was close, lasted for more than an hour, and required Swiatek to overcome a 0-2 deficit and save 7 out of 8 break points before finally advancing on the fourth set point.
With her continuous pressure with powerful forehands, Swiatek won the tenth game in a row and advanced 4-0 in the second set.
The former world number one lost her momentum briefly, as Frech broke her serve, but she regained her balance to qualify for the round of 16, where she awaits one of the two players qualified from the lucky losers, Thailand's Lanlana Tararudee or American Ashlyn Krueger.
British Sonay Kartal, ranked 170th in the world and who missed six months this year due to a stress fracture in her spine, surprised Swiss Belinda Bencic, the ninth seed, and defeated her 6-0, 7-5 to secure a date with Italian Jasmine Paolini (15), who won against Czech Nikola Bartunkova 7-6 (7-5), 6-3.
Eva Jovic (10) won against Ukrainian Dayana Yastremska 6-4, 6-1, while the latter's compatriot Elina Svitolina (5) succeeded in overcoming the obstacle of Russian Liudmila Samsonova by defeating her 6-2, 5-7, 6-2.
Czech Karolina Muchova (6) won in a marathon match against American Katie McNally 3-6, 7-6 (7-1), 7-6 (7-4), and Russian Diana Shnaider (11) won against Kazakhstan's Yulia Putintseva 6-2, 6-2.
Medvedev passes Tsitsipas and reaches Shanghai tennis quarter-finals
Russian Daniil Medvedev, ranked sixth in the world, reached the quarter-finals of the Shanghai 1000-point Masters tennis tournament for the fourth time in his last five participations, after eliminating Greek Stefanos Tsitsipas by defeating him 6-4, 7-5 yesterday, Wednesday.
Medvedev, who is seeking his second title in this tournament after the one he won in 2019, confirmed his superiority over Tsitsipas after achieving his eleventh victory over the Greek in 16 confrontations.
Medvedev said, "I love Shanghai as a city. It is one of my favorite stops on the tour (season tournaments), so I try to stay in it as long as possible. I am playing at a great level."
Medvedev performed remarkably on his serve and did not give his Greek opponent any chance to break, and was also more consistent from the back of the court, committing eight fewer unforced errors than his opponent (10 vs 18).
By winning within one hour and 24 minutes, Medvedev became only the sixth player to reach the quarter-finals in Shanghai four times or more.
The Russian aspires to win his fourth title this year and his first in 1000-point Masters tournaments since 2023.
In the next round, he will face American Tommy Paul or Belgian Zizou Bergs, who eliminated world number three Carlos Alcaraz on Monday.
Medvedev has not lost any set so far in Shanghai, and his current run boosts his hopes of qualifying for the ATP Finals in Turin.
The 30-year-old player occupies the eighth and final spot qualifying for Turin 2026, and seems to be in a good position to participate in the final tournament for the seventh time in his career.
Rising Spanish star Rafael Jodar received a warning for "unsportsmanlike conduct" after shouting a profanity at a ball boy, on his way to reaching the quarter-finals.
Jodar, the 20-year-old, was trailing against Dutchman Botic van de Zandschulp after losing the first set in the tie-break when he shouted, "Give me the f***ing towel!"
Jodar hit a long shot and lost a break point in the first game of the second set.
Jodar quickly received a warning for unsportsmanlike conduct, a violation of the ATP rules, by Ecuadorian umpire Jimmy Pinoargote.
The two exchanged words in Spanish as Jodar complained to Pinoargote about his request for the towel being ignored.
Pinoargote replied that he understood Jodar's position but could not excuse him for the word he used.
Pinoargote said, "Ask, and I will ask him," adding, "Not like that, that's not how we talk to them."
When Jodar asked Pinoargote, "What did I say?" the umpire replied, "I cannot repeat it, you know what you said."
Jodar turned his one-set deficit against Van de Zandschulp into a well-deserved 6-7 (4-7), 6-4, 6-2 victory.
Jodar, ranked 13th in the world, is having a distinguished season that he started in 168th place.
He will face Casper Ruud in the Shanghai quarter-finals after the Norwegian qualified following the withdrawal of Canadian Felix Auger-Aliassime due to injury from the fourth round.
