Jennifer Brady, the 13th seed, saw her French Open hopes dashed in cruel fashion after suffering an injury - but her opponent Coco Gauff made a special gesture.
Gauff, seeded number 24 for the tournament, played some sublime tennis in the opening set to dominate proceedings in very impressive fashion.
The 17-year-old dropped just a solitary game to Brady in a first set which lasted just 23 minutes on Court Suzanne Lenglen.
French Open women
Impressive Krejcikova beats Gauff to reach semi-finals
But at the changeover between sets, suddenly the match ended abruptly as a tearful Brady realised she could not continue with reported bone bruising.
In a very sporting act, Gauff walked over and gave her fellow American a big hug before applauding her opponent off the court.
Brady simply said to Gauff: "I'm so sorry!"
- Defending champion Swiatek roars on at Roland Garros
- 'It's reasonable' - Umpire defends Nadal with Norrie angry at delays
- 'Not many people know this' - The Nadal stat 'vital' behind his success - Evert
'I hope we can help her' - Gauff reacts to Osaka's French Open withdrawal
"Well this is a sad sight. Brady is looking very glum and the emotion is getting to the older of the two Americans here," said Eurosport commentator Barry Millns.
"Oh dear, oh dear! I'm afraid that is it. She is not going to play any more. She did have a left foot injury in room - whether that is the reason why, we will find out in due course.
"But that, I'm afraid, is as far as she can go at Roland Garros and we will wish her a speedy recovery. A real disappointment for her."
"Gauff was playing beautifully in that first set, almost perfectly."
New York Times tennis writer Christopher Clarey reported that the reason for her retirement was a foot problem - a plantar fasciitis and a potential bone bruise - and she was in too much pain to continue. Brady reportedly considered not playing the French Open because of the injury.
Eurosport expert Annabel Croft added: "That is a great shame. A great, great shame. It does help Gauff with her energy levels moving forward and she will be happy with what she put out."
Gauff will next take on Ons Jabeur in the fourth round as she looks to continue her progress at Roland Garros.
- - -
Watch all the action from the 2021 French Open live on Eurosport, eurosport.co.uk and the Eurosport app with 13-time champion Rafael Nadal eyeing a remarkable 14th title and 2020 Roland Garros sensation Iga Swiatek aiming to replicate her stunning triumph.
Flawless Gauff cruises past Jabeur to reach French Open quarter-finals
Gauff scoops both singles and doubles title in Parma