There was reason for Raducanu to be confident against Zheng, who is still finding her feet on the grass court and has a serve that can waver when under pressure.
Raducanu had also made relatively serene progress through her first two matches, dropping just eight games across four sets.
But, as Raducanu found against Iga Swiatek in Melbourne and Paris, and Coco Gauff in Italy, there is a different, consistent level needed to beat the players for who winning is a habit.
In an edgy start, Raducanu put pressure on Zheng’s serve while saving break points in her own games.
But Zheng broke through at the seventh attempt, a blistering backhand down the line silencing the crowd, who had earlier voiced their displeasure after Zheng had to change her shoes midway through the game.
Raducanu kept up the pressure, creating an immediate break-back opportunity, but Zheng’s huge groundstrokes kept her at bay, and a rushed forehand into the net handed the top seed the first set.
Raducanu left court for a medical timeout on her back, having struggled with back spasms before and after Roland Garros, but took advantage as Zheng’s first serve all but disappeared.
With the wind picking up, Raducanu produced a series of ruthless returns to Zheng’s second serve and quickly found herself a double break up thanks to some strong serving.
But Zheng wrestled a break back and upped her intensity when needed, creeping forward to attack Raducanu’s serve. A double fault handed Zheng the break back and she reeled off four games in a row to close out the match.
Despite the loss, there will be enough for Raducanu to be confident she can perform well on the grass – but she will know there is still a gap to be bridged when it comes to challenging the very best.