Emma Raducanu retired from her match against Ann Li after needing her blood pressure and other vitals taken at the Wuhan Open.
The 22-year-old looked out of sorts and required a medical time out at 6-1 4-1 down, before eventually calling a premature end to the match.
Raducanu, the world No 30, broke Li in the opening game but her opponent stormed back to win six in a row. Raducanu appeared dizzy at points during the second set before medical assistance was raised.
Conditions on court were difficult, with humidity at 60 per cent and the temperature around 35 degrees.
“First I want to wish Emma a fast recovery. Not sure what [happened], but looked like she wasn’t feeling good,” Li said afterwards.
”But yeah, tough match last time so I knew it was going to be tough but I wish her to feel better. I’m happy with my performance.”
Tennis broadcaster Jonathan Overend, commentating on Sky, said: “I do feel maybe she should have called for attention earlier in the match when it was clear that she wasn’t feeling herself.”
Li, ranked 16 places below Raducanu at 46 in the world, will take on ninth seed Ekaterina Alexandrova in the second round.
More to follow
08:01 AM BST
Raducanu retires
After being seen to by the WTA physio and tournament doctor, Emma Raducanu has retired in Wuhan.
There were periods during the match when the 22-year-old was not attempting to chase after balls, which is uncharacteristic. Raducanu was struggling with the humid conditions and was looking weary at times on court in both sets.
The Briton was trailing 6-1, 4-1.
07:59 AM BST
Trainer and tournament doctor tending to Raducanu
Raducanu is currently being seen to by the WTA physio.
The Briton is having her temperature taken and blood pressure checked.
The tournament doctor is also checking her pupils and heart rate.
07:55 AM BST
Raducanu* 1-6, 1-4 Li
Another wayward forehand costs Raducanu the opening point before the Briton gets to 15-15. The pair then exchange the next two points before Raducanu throws in another forehand error to give Li break point.
The American nets a forehand return as the score moves to deuce. Li then pushes a short forehand long but Raducanu is unable to secure the game as she throws in an error of her own.
Second break point for Li and Raducanu concedes the game with another double fault.
07:48 AM BST
Raducanu 1-6, 1-3 Li*
Raducanu crushes a forehand return for a clean winner before some good serving sees Li move to 40-15.
The American holds with ease to extend her lead in this second set.
07:45 AM BST
Raducanu* 1-6, 1-2 Li
Raducanu, looking to force the issue, quickly falls 15-30 behind before Li gets to 15-40 and breaks with another forehand pass. The Briton seems to be struggling physically.
07:43 AM BST
Raducanu 1-6, 1-1 Li*
Li gets to 30-0 before throwing down a double-fault as Raducanu gets on the board at 30-15. The Briton then gets to 30-30 before taking on the Li serve and winning to move 30-40 ahead. Li saves the break point to move to deuce before dumping a backhand into net to give Raducanu another break point.
Li cracks a forehand down the line for a clean winner to move the score back to deuce. The American eventually holds after saving a couple of break points.
07:37 AM BST
Second set: Raducanu* 1-6, 1-0 Li
Raducanu loses the opening point before getting on the board at 15-15. Raducanu crushes a forehand cross to move to 30-15 before setting up the next point with a well-placed first serve. The Briton then loses the next point as she appears dazed on the Wuhan Centre Court.
A Raducanu double-fault at advantage sees Li get back to deuce. The Briton then throws in another to give Li a break-point look. Li nets a forehand before Raducanu cracks a forehand winner to get back to advantage. Another double-fault moves the scoreboard back to deuce but the Briton does eventually hold.
07:26 AM BST
Li wins the first set 6-1
Li starts the game with an ace before Raducanu goes wide with a forehand return as Li moves to 30-0. The American throws down her fourth ace to move to 40-0 before Raducanu gets on the board at 15-40.
The American holds to 15 to close out the first set. Very impressive stuff from the 25-year-old.
07:24 AM BST
Raducanu* 1-5 Li
Li finds an incredible angle with a forehand winner to move 0-15 ahead. The American then moves to 0-30 before Raducanu nets a backhand to fall 0-40 behind. Li nets a backhand approach to give Raducanu a lifeline. 15-40.
A good serve sets up the next point for the Briton as she gets to 30-40 but Li does win the next point to take a 5-1 lead.
07:18 AM BST
Raducanu 1-4 Li*
Li starts the game with an ace and then places a forehand in the open court to move 30-0 ahead.
The American holds to love for the second service game in a row.
07:16 AM BST
Raducanu* 1-3 Li
Li pushes a forehand return long before Raducanu goes long on the same wing to move the scoreboard to 15-15. Li then finds a forehand pass to move 15-30 ahead. The American then finds the line again to bring up two break points. Raducanu saves the first... and the second as Li goes long with a forehand on the run.
Raducanu then nets a forehand to give Li advantage and another break-point look and the American breaks again.
07:10 AM BST
Raducanu 1-2 Li*
Li, showing off her big forehand, races to a 30-0 lead before a classy cross-court passing shot brings up three game points. The American holds to love and takes the lead in this opening set.
07:07 AM BST
Raducanu* 1-1 Li
Raducanu starts the game with a backhand winner before seeing a forehand sail long. The Briton then goes long with another forehand to fall 15-30 behind. Li then deploys a nice slice backhand that puts Raducanu in trouble at the baseline and the American gets the break back.
07:04 AM BST
First set: Emma Raducanu 1-0 Ann Li*
Raducanu, returning at 30-40 crushes a backhand cross-court to get to deuce, before going wide with a forehand to give Li advantage.
Some good retrieving gets Raducanu back to deuce before the Briton comes out on top of an extended rally to get to advantage. Li saves break point.
The American then throws in a double fault to give Raducanu a second break point and this time the Briton does break with a great forehand volley.
06:53 AM BST
Coin toss
Ann Li won the toss and has elected to serve first.
06:51 AM BST
Players are on court
Ann Li enters the court first followed by Emma Raducanu.
06:48 AM BST
Raducanu and Sabalenka hit together
Ahead of their first-round matches in Wuhan, Emma Raducanu and world No 1 Aryna Sabalenka hit together on the main court.
06:43 AM BST
Osaka moves on
Naomi Osaka is through to the second round in Wuhan after seeing off Leylah Fernandez in three sets.
06:32 AM BST
Second meeting of the year
Good morning and welcome to first-round coverage of Emma Raducanu versus Ann Li at the Wuhan Open.
The British No 1 is 2-2 so far in Asia. She beat Jaqueline Cristian in Korea before going down in three sets to Barbora Krejcikova. In Beijing, she saw off Cristina Bucsa in the second round after receiving a first-round bye as one of the top 33 seeds, before succumbing to Jessica Pegula, again in three sets, in the third round.
Raducanu had match points in both defeats – three against Pegula and two against Krejcikova – but was unable to convert.
Speaking about those tough losses ahead of her opening match in Wuhan, Raducanu said: “The second match, I found it easier to get over than the first because I know I was playing some better tennis and just improving with my level.
“I feel like I didn’t take too long to kind of dwell on it and just got straight back to work. And I do feel like I’m improving and making progress. I still see the differences in where I want to go but I know I’m doing good work day-to-day to try and get there.”
Li is still searching for her first win of the Asian swing. The 25-year-old American world No 46 has not won a match since the US Open, where she made a run to the round of 16.
Raducanu, currently ranked 30th in the world, leads the head-to-head 1-0. Their first and only meeting was earlier this year on the grass at Eastbourne. The Briton came back from a set down to win 6-7, 6-3, 6-1.
Russian ninth seed Ekaterina Alexandrova awaits in the second round.