BEIJING - The head coach of China's all-conquering men's table tennis team has warned Olympic and world singles champion Zhang Jike to knuckle down at the Asian Games or risk throwing away his chance to defend his gold medal at the Rio Games.

Though the 26-year-old has been virtually untouchable in singles since his 2011 world title in Rotterdam, his lacklustre performances in team events have been a source of frustration for long-serving coach Liu Guoliang.

China won the world championships team event in Japan in May but Zhang was swept 3-0 by Germany's Dimitrij Ovtcharov in his rubber of the final, and also had a surprise loss to Taiwan's Chen Chien-an at last year's World Team Classic in Guangzhou.

Liu cautioned the Qingdao-born paddler, the fastest winner of the 'grand slam' of Olympic, world championship and world cup table tennis' titles, against complacency and said his team mates were eyeing his place for the Rio singles.

"I gave him some reminders and even warnings about his position," Liu told local media. "In the nearly two-year period to Rio, the competition will be fierce. He really can't make have a mistake.

"(World number two) Fan Zhendong and (number one) Xu Xin are also a chance (to win the grand slam) and I believe their ability now is the same as it was for when Zhang won his."

Liu said Zhang had been dogged by questions about his sense of team camaraderie and responsibility over the past two years, and that "the problems had not been fundamentally solved".

"Some of his performances on court have been listless ... He has appeared like he doesn't care and has actually given me the feeling his heart's not in it. I felt that was obvious at the championships in Japan."

Boasting all of the men's top four in singles and six of the top seven in women's singles, China are almost certain to dominate the Asian Games tournament at Incheon, but Liu was adamant he would come down hard on any weak links.

"In the Asian Games team component, (Zhang) can't make any mistake," he said. "With every loss there's danger. By the time he feels that danger, it might be too late for him."