General view, JULY 21, 2021 - Tennis : Men's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Naoki Nishimura/AFLO SPORT)

Novak Djokovic (SRB), JULY 21, 2021 - Tennis : Men's Training Session during the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by YUTAKA/AFLO SPORT)

Novak Djokovic (SRB), JULY 21, 2021 - Tennis : Men's Training Session during the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by YUTAKA/AFLO SPORT)

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DuxXiaoyi PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DaixTianfang PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia arrives for a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DaixTianfang PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DuxXiaoyi PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DuxXiaoyi PUBLICATIONxNOTxINxCHN

Sport Bilder des Tages 210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DuxXiaoyi PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DaixTianfang PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia reacts during a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DuxXiaoyi PUBLICATIONxNOTxINxCHN

210721 -- TOKYO, July 21, 2021 -- Novak Djokovic of Serbia attends a training session prior to the Tokyo 2020 Olympic Games, Olympische Spiele, Olympia, OS at Ariake Tennis Park in Tokyo, Japan, on July 21, 2021. TOKYO2020 JAPAN-TOKYO-OLY-TENNIS-DJOKOVIC-TRAINING DaixTianfang PUBLICATIONxNOTxINxCHN

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

Naomi Osaka (JPN), JULY 19, 2021 - Tennis : Women's official training before the Tokyo 2020 Olympic Games at the Ariake Tennis Park in Tokyo, Japan. (Photo by Yohei Osada/AFLO SPORT)

15 July 2021, Argentina, Buenos Aires: Tennis player Florencia Moreno from Argentina in action during a training session. Moreno is the first Argentine woman to qualify for the Paralympics in wheelchair tennis. "To be part of it is a dream," says the tennis player. Photo: Florencia Martin/dpa

FILED - 15 July 2021, Argentina, Buenos Aires: Tennis player Ezequiel Casco from Argentina in action during a training session. Photo: Florencia Martin/dpa