HANGZHOU - Olympic and world champion Sun Yang is preparing for the Barcelona FINA world championships without his long time mentor Zhu Zhigen following their falling out.

Right now Sun trains in Hong Kong, under former Chinese head coach Zhang Yadong.

"I will get rid of all distractions and go all out to prepare for the worlds," the Olympic 1,500m freestyle winner wrote on his microblog.

Zhang is pleased with Sun's training. "He is focused and finding back his form," Zhang said in an telephone interview on Wednesday.

Sun became the first Chinese man to win an Olympic swimming title in London last year. He set a world record in the 1,500m to win in Shanghai worlds in 2011 where he also triumphed in the 800m free.

But he only registered for 400m and 1,500m events in the world championships.

"Sun Yang only had two events registered. We are concerned that he is not able to perform well as he has lacked systematic training the past six months,"Chinese swimming association deputy head Shang Xiutang was quoted. "We are even not so sure about these two events now."

But Zhang told Xinhua that registrations may change as Sun is getting in shape.

The 22-year-old, rocketing to join China's top sporting stars basketball giant Yao Ming and tennis queen Li Na, once again became headline figure at the beginning of this year with a public row with coach Zhu Zhigen.

Sun refused to train after he fell in love with an air hostess and threatened to split with Zhu when the coach told him to refrain from this romantic relationship.

Though the two parties put on a gesture of reconciliation under the mediation of swimming authorities, Sun once again requested to part ways with Zhu after 10 years of training with him.