Li Na has put her dream run to the semi-finals of the Australian Open down to a rigorous off-season training regime that almost forced her to quit the sport.
The Chinese 30-year-old reached her first grand slam semi-final since winning the 2011 French Open with a 7-5 6-3 victory over Agnieszka Radwanska, ending the Polish fourth seed's unbeaten 13-match run to start the year.
Li has struggled in the majors since her breakthrough at Roland Garros two years ago, failing to advance past the last 16 in any of them.
But a change of coach last August, from her husband Jiang Shan to Carlos Rodriguez, the former trainer of ex-world number one Justine Henin, has her physically - and mentally - better prepared to continue to challenge the top players in the game.
"He was very tough with training in the winter - it was unbelievable," said Li, who joked that she considered quitting after just three days.
"I said to him, 'Do you know how old I am?'. He was thinking I was 20 years old."
She added: "We train every day for five, six hours, but not only playing tennis. Tennis was like maybe two, three hours. Fitness was for two or three hours as well.
"First time I was training with him, I was so excited, but after three days, I was dying. My husband didn't come with me to Beijing.
"I called him and said, 'Carlos is crazy'. He was like, 'Why?' I described the program to him. He was like, 'Don't joke'. I said, 'Hey, listen, I'm not making a joke'."
That fitness paid off in spades for the sixth seed on Tuesday, needing one hour and 42 minutes to get past Radwanska to avenge her loss to the Pole in the semi-finals of the lead-up tournament in Sydney.
"She's a tough player," Li said. "I was feeling today against a wall. She can hit everywhere, but without a mistake. You have to focus on every shot. Not every point, every shot."
Li hit 32 winners but also made 40 unforced errors and will need to up the ante against Maria Sharapova on Thursday.
The world number two continued her stroll through the tournament with a 6-2 6-2 win over fellow Russian Ekaterina Makarova.
"To win a Grand Slam, you have to win seven matches - doesn't matter if you're lucky or unlucky, you still have to win seven matches," said Li, who will return to the top five when the new rankings are released next Monday."Before I thought, 'If I win who will I play in the fourth round or fifth round'. Now I've changed - I didn't look at the draw, I just take it match by match."