(CNN) -- Last week world No. 1 Novak Djokovic wanted to win this year's French Open to complete his collection of grand slam titles, now he wants the trophy for a more pressing reason -- to honor the death of his "second mother".
Jelena Gencic, who coached Djokovic for five years from when he was just six, died on Saturday.
The potential impact of the 77-year-old's death on her Serbian compatriot was deemed to be so great that Djokovic's management team kept the news from him until after he had beaten Grigor Dimitrov in Saturday's third round.
Djokovic's reaction backed up their assessment as the 26-year-old canceled his post-match news conference, issuing an apology to the media as he did so.
On Monday, he paid tribute to his mentor shortly after seeing off Philipp Kohlschreiber 4-6 6-3 6-4 6-4 to reach this year's quarterfinals at Roland Garros.
"She's one of the most incredible people I ever knew," he told reporters. "Jelena was my first coach and was like my second mother.
"We were very close throughout my whole life and she taught me a lot of things that are part of me, part of my character today. I have the nicest memories of her and these will stay with me forever.
"I think it was the right thing to give me the news after the match (against Dimitrov)," he added. "Regardless of the timing, it was still a shock."
A beaten finalist in Paris last year -- when he lost out to Roland Garros record breaker Rafael Nadal -- Djokovic last saw Gencic in February, shortly before the start of the Dubai Open.
Yet his last conversation with a woman who also helped develop the talents of grand slam champions Goran Ivanisevic and Monica Seles came far more recently.
"I remember the last conversation we had two weeks ago about Roland Garros, and she told me, 'Listen, you have to focus, you have to give your attention to this tournament. This is a tournament you need to win.'
"She was giving me this kind of inspiration and motivation even more. So now I feel in her honor that I need to go all the way.
"But it's not about me only. There are so many great players still around in the tournament. It gives me that inner strength to push even harder."
In a recent interview, Gencic said she spotted Djokovic's potential almost from the moment she first met him in Belgrade.
"When I met him I knew immediately that he was different. I told his father that he was an exceptional talent and that one day he will be a big champion," said a woman who represented the former state of Yugoslavia at both tennis and handball.
After he won Wimbledon for the first -- and to date -- only time in 2011, Djokovic visited Gencic as part of his celebrations.
And the world number one says Gencic, who was recently battling breast cancer, has inspired him to work with young tennis players in the future.
"She was 77 years old, and before she passed away two days ago, last week she was giving lessons to kids," he said.
"I hope to follow on from where she stopped. She gave so much knowledge and I feel I have a responsibility to carry on that work.
"She never married, never had children. She was dedicated to tennis, the kids and coaching."
"I know that her spirit will be always with me and always on the tennis court, because this is what she always loved to do. It's her favorite place in the world and I'll make sure that her legacy continues."
If the Serb is to provide his perfect send-off for Gencic by winning Roland Garros for the first time - and thus become only the eighth man to achieve the career grand slam - he must first beat Tommy Haas, who is also chasing history.
When the number 12 seed beat Russia's Mikhail Youzhny, the German became the oldest man to reach the quarterfinals of a grand slam since Andre Agassi in 2005 and the oldest to do so in Paris since 1971.
Once ranked number two in the world, Haas, 35, missed the entirety of the 2013 season after twice undergoing should surgery -- but is now one of four players over 30 in the quarterfinals along with Roger Federer, David Ferrer and Tommy Robredo.
"I think we all just are smarter about how we train, about how we eat, about how we do recovery," he said.
"The physical and fitness areas have improved a lot in sports in general. I think that's why you see maybe more people also in the early, mid-30s doing well."
At least one man over the age of 30 will reach the semifinals, since Ferrer and Robredo meet in the quarters, while Federer will take on local hope Jo-Wilfried Tsonga, a relative strapling at the age of 28.
Age was also on the minds of those watching Rafael Nadal on Monday, with the Parisian crowd singing 'Happy Birthday' to a man who celebrated his 27th birthday in style.
Bidding to become the first man in tennis history to win eight titles at the same major championship, Nadal won 6-4 6-1 6-3 against 13th seed Kei Nishikori, the first Japanese man in the fourth round since Fumiteru Nakano in 1938.
"It's a very special moment," said Nadal of the crowd's decision to break into song. "Kei is a great player and he is getting better every season. But today I think I played my best match of the tournament."
Nadal will play Stanislas Wawrinka in the quarterfinals after the Swiss beat Frenchman Richard Gasquet in a thrilling match, with the ninth seed rallying from two sets down to win 6-7 4-6 6-4 7-5 8-6.