In April, he clocked 51.86 in the National Championships, just 0.01 shy of the world record.

"When I finally tasted victory at the worlds, I suddenly felt a bit nervous," he said. "After the semifinals yesterday, I thought that it was possible to beat the world record, but I didn't give myself any surprise, which I felt a little disappointed about."

"My results have progressed in a consistent way. I could have hit the benchmark of 52 seconds back in Rio, but I was too nervous in major tournaments to perform at my normal level. This time, I was also quite nervous here and could only win by a small margin.

"I won the title by only four hundredths of a second, and I met tough challenge to resist the pressure from other opponents," Xu said, suggesting that he felt a little frustrated with his performance in the final.

Minutes before, Chinese swimming ace Sun Yang added his first 200m freestyle title to his title collection from four world championships, which also includes 400m, 800m and 1500m.

Sun gave an emotional Xu a warm hug after the latter's ice-breaking victory.

"I can also stand at the stage center now, just like he did," said Xu, scheduled to compete later in the 50m and 200m backstroke in the Hungarian capital, said with great confidence.

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