Raducanu still has two events on her schedule this year – the Tokyo Pan Pacific Open and the Hong Kong Open.
Frances Roig has reached an agreement with Raducanu to coach Raducanu until the end of the season, but he is not with her in Ningbo.
Raducanu has played 50 matches on the WTA Tour this year, her most since her breakthrough victory at the 2021 US Open.
The physical demands may have started to show, with Raducanu’s athleticism declining and former top-40 player Zhu extending her rallies to keep her on the court longer.
Raducanu’s first-serve scoring rate was only 51%, and his second-serve scoring rate was 38%.
Despite breaking serve four times in the final five games, she took a 3-0 lead and held on to hold on to the first set.
She and Zhu traded break opportunities early in the second set before Raducanu called in a physical therapist. She left the courtroom after Zhu forced the ruling.
Raducanu caught her back after a forehand run early in the third set, and she made more mistakes as the match wore on.
Zhu will face Russian top seed Mira Andreeva in the round of 16 on Wednesday.
