TOKYO: Daniil Medvedev gave a frank assessment of the stifling conditions for Olympic tennis on Wednesday when the visibly upset Russian told the umpire he could finish his match but wanted to know who would take responsibility if he died.

The International Tennis Federation, in charge of the competition at the Games, said matches will begin from 3 pm local time from Thursday, instead of the scheduled 11 am start.

"In the interests of player health and welfare and following extensive consultation, the ITF has announced a change of schedule due to the increasing heat and humidity currently being experienced in Tokyo," the governing body said.

Medvedev was the first player to appeal for a delayed start and received support from world number one Novak Djokovic.

The Serbian won his singles in better conditions in late afternoon before returning to register a mixed doubles victory. 

"Tennis needs to be considered as one of the endurance sports," the 20-times Grand Slam winner said.

"I am playing tennis professionally for 20 years and I've never faced these kind of conditions in my entire life on a consecutive daily basis."

Second-ranked Medvedev opened proceedings at 11 am on Ariake Tennis Park's main show court against Italian Fabio Fognini.

The 25-year-old took a medical timeout on court and called the trainer on two other occasions, and chair umpire Carlos Ramos asked Medvedev if he was alright during the second set.

"I'm fine. I can finish the match but I can die. If I die will the ITF (governing body International Tennis Federation) take responsibility?" Medvedev replied.


COLD SHOWER

The ITF's "extreme weather policy" allows a 10-minute break between the second and third sets if agreed by both players and Medvedev used that time to get a freezing cold shower.

"Even from the first set I didn't feel good enough with my breathing. That's why I called the physio, I felt like my diaphragm was blocked," he said.

"And then in the second set, I just had darkness in my eyes, like between every point, I didn't know what to do to feel better."

While Medvedev said he was "lucky" he could continue his match to advance, Spain's Paula Badosa gave up after suffering heat stroke during her match against Czech Marketa Vondrousova.

She needed a lengthy medical timeout but was unable to recover and left the court in a wheelchair.

The year has been tough for the Spaniard, who was the only player at the 2021 Australian Open to contract COVID-19 in the leadup to the major.

"It's a shame to end my participation in this way. It's been a tough ask since day one, we tried to adapt as best we could but today my body hasn't held up as it needed to," said Badosa.

"I suffered heatstroke ... I didn't feel like I could carry on with the game."