MELBOURNE - When Hsieh Su-wei is in fine form, something fantastic occurs: an outbreak of joy follows. Oohs follow aahs. A public swooning occurs. A thousand smiles break out. In this mostly one-dimensional, baseline-bashing, one-pace universe she's an oddity. She plays tennis, all of it. Or at least shows us there's another way to play the game.
Or as Naomi Oaska, world No. 4, who finally beat her 5-7, 6-4- 6-1, said: "I walked into the match knowing that she was going to do a lot of strange things, no offence."
Hsieh is world No. 27, 33 years old, all brain and no bicep, and operates at a different speed than Osaka does. The Japanese player's average first-serve speed was 167kmh, the Taiwanese player's was 135. Ah, but Hsieh reminds us of a word that tennis has somewhat lost.
She can drop shot and drop volley and is drop-dead smart. She blocks balls, stabs at them, underspins them and has a degree in voodoo - what else explains her ability to be in the very place that her rival has decided to hit the ball.
She's as slim as Merlin's wand and works more angles than a conman. She moves like a fleeing cat and invents on the move. She hits two-handed on both sides and works every side of her brain. At one point she returned a smash with a lob that was almost a winner.
Later, asked if she'd ever tried the shots Hsieh plays, Osaka said: "I have never really seen anyone hit that way."
Up in the stands Japanese reporters were scribbling furiously. Either taking notes or composing haiku. For a while Hsieh was in such command that Osaka looked like someone trying to solve a Rubik's Cube, one-handed, in the dark. "I can never really tell where she's going to put the ball," said the Japanese.
Patience is not Osaka's game and yet serenity is the way to solve Hsieh. "I just felt like she was playing too good," said the Japanese, "and I had to wait. For me, it's a bit difficult to do that because my patience isn't so great on that side, to be honest. But I just felt like I had to trust - like, I did a lot of off-season training like running, so I just felt like I had to trust my athleticism, in a way."
Eventually she found her way because eventually the Japanese, even at 21, is that good. Last year Hsieh defeated Garbine Muguruza at the Australian Open and Simona Halep at Wimbledon because her game is unfamiliar. She asks questions that even top players can go a year without facing.
In a way she's more than an opponent, she's a unique examination. A tennis test. And Osaka did well to pass. Hsieh led 7-5, 4-2, 40-0 but said, "I started thinking too much", and then Osaka started hitting too well.
Osaka stays in the tournament but Hsieh deserves to remain in the memory. We come to this Open because we're besotted by rankings and earnings, history and head-to-heads, winners hit and percentage of first serves. But when Hsieh starts to play we remember that this Open is not just a tennis competition but also a celebration.