Qualifier Olga Danilovic hails 'out of this planet' compatriot Novak Djokovic
Danilovic, ranked 125, needed more than three hours to defeat Croatia's Donna Vekic 0-6, 7-5, 7-6(8) in the French Open third round, playing the first match of the day at 11am.
On Thursday, she spent two and a half hours on court to see off 11th seed Danielle Collins in another three-setter which didn't finish until 6.30pm.
The Serb has already played six matches at the tournament, a gruelling effort which left her in tears during her on-court interview on Friday.
Danilovic praised the mental resilience of Djokovic for helping inspire her to a landmark appearance in the second week of a Grand Slam.
"The mentality he has, we are all seeking to have that. It's just something that is out of this planet," said Danilovic who admitted that playing with the 24-time major winner at the United Cup earlier this year had been a "bucket list moment".
"I don't know if we actually appreciate that he's the best player in the world by far. He's a very humble and nice guy, especially that he's No. 1 in the world and he's, for me, the greatest of all time.
"He's really proud to represent our country, he's really open for us to talk. I come to him with some day-to-day struggles that I have on court, and he's really happy to share his thoughts with me and what he learned, what kind of mistakes he did so maybe I don't have to do them."
On Friday, the left-handed Danilovic was just two points from defeat against 40th-ranked Vekic, a two-time Grand Slam quarter-finalist.
Vekic served for the match at 5-4 and 6-5 - holding a 30-0 lead the second time - and then led 6-2 in the final set super-tiebreak.
But Danilovic's bolder approach paid off as she hit more winners, 29 to Vekic's 15 in the deciding set.
"Those were tears of relief and happiness," Danilovic, who also made the third round in 2023 out of qualifying, said as she explained her tearful on-court interview.
"We played for three hours and eight minutes. Your heart is going to get up, because being in that level of stress for three hours and eight minutes, I don't know if it's healthy at the end of the day."
Danilovic is becoming something of a sensation of qualifying rounds at tournaments.
As a lucky loser at the 2018 River Cup in Moscow she became the first player born in the 2000s to win a WTA singles title.