Lin Zhu actually knew who the man was. The first badminton video he watched as a child was that of the man. At that time, the man was playing in All England and managed to come out victorious after beating another athlete from England.
Back then, little Lin Zhu could only utter the word "Woah" with his lips when he witnessed how well the man played on the court. His power, speed, coverage, and determination were impeccable, and that's why the athlete from the host country couldn't do anything before admitting defeat.
Lin Zhu could see that the man named Ye Jiang was indeed a genius athlete who could play beautifully on the court, even the man's smile when receiving trophies and prize money was also very beautiful in Lin Zhu's eyes.
Just in case you don't remember, Ye Jiang's name was mentioned in the first chapter :)