Tennis: Nadal turns 27, thumps Nishikori to enter last 8

PARIS (AFP) - Seven-time champion Rafael Nadal celebrated his 27th birthday on Monday by trouncing Japanese 13th seed Kei Nishikori 6-4, 6-1, 6-3 to reach tennis' French Open quarter-finals.

Next up for the Spanish defending champion is either French seventh seed Richard Gasquet or Stanislas Wawrinka, the Swiss ninth seed.

Earlier, world No.1 Novak Djokovic paid an emotional tribute to his first coach, Jelena Gencic, who died at the weekend, hailing her as his "second mother".

The 77-year-old nurtured the young Serb's talent when he was six years old and with the agreement of his parents, trained him for five years before he left for further coaching in Germany.

She also coached fellow Grand Slam champions Monica Seles and Croatia's Goran Ivanisevic.

"Jelena was like my second mother and we were very close. She taught me many things," said Djokovic, after seeing off Philipp Kohlschreiber 4-6, 6-3, 6-4, 6-4 to reach the quarter-finals.

"The things that she taught me are part of my character and I have the nicest memories of her and these will stay with me forever."

Djokovic, who last saw Gencic in February as she battled breast cancer, said he wants to carry on her work with youngsters.

"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. She didn't care about her illness."

Djokovic's coaching team and support staff deliberately kept the news of Gencic's death from him until he defeated Grigor Dimitrov in Saturday's third round.

Gencic said in a recent interview that 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," she said.

After winning Wimbledon in 2011, Djokovic visited her in Belgrade to celebrate the win.

Djokovic, who is seeking in Paris to become just the eighth man to win all four Grand Slam titles, will face Germany's Tommy Haas for a place in the semi-finals.