The two had met just three weeks earlier in the semifinal of the Asia Championships. Not much split the pair as Yamaguchi came from one game down to win 15-21 21-16 21-17.
The scoreline was eerily similar in Nanning, only this time it was Chen who came from behind.
Heading into the contest, Yamaguchi led the head-to-head 9-5. The last three, however, had gone to three games with Chen winning two of them – at the Japan and China Opens last year.
It was also a meeting of the two in-form players of the season. In eight tournaments prior to the TOTAL BWF Sudirman Cup 2019, Yamaguchi had two titles, one runner-up finish, and three semifinals. For Chen, it was two titles and three semifinals.
Chen had slightly the tougher week in Nanning, playing in three singles matches leading into the final (Soniia Cheah, Saina Nehwal, Mia Blichfeldt). The fact she was not required against Ratchanok Intanon in the semi against Thailand was perhaps a blessing.
Yamaguchi, by comparison, was rusty in her opening singles loss to Pornpawee Chochuwong 21-9 14-21 20-22, but then consolidated with an emphatic 21-13 21-13 win over Gregoria Mariska Tunjung.
It did, however, only give her 24 hours to recover before the crucial clash with Chen.
The final was a seesawing battle across 81 minutes with both players holding the ascendency at different stages of the match and then relinquishing it under pressure.
BWF commentator Morten Frost noticed while on air that Yamaguchi was at times extremely “erratic” and would often “go into her shell” at various stages.
The evidence was in the scoreline as Yamaguchi led 10-6 in the first game before conceding eight consecutive points to hand Chen the lead at 14-10.
Yamaguchi squared it at 15-15 only for herself to reel off six straight points to take the first game 21-17.
The second game followed a similar path but this time it was Chen who got the wobbles. She led 5-1 and 7-2 only to allow Yamaguchi back in it to trail 9-10. But the unforced errors continued from Yamaguchi’s racket and the less-experienced Chen was finally able to capitalise to open up a 16-11 lead.
Frost had before the match predicted that Yamaguchi’s greater experience in these pressurised ties would serve her better, but it was, in fact, Chen who raised her play and was able to close out the second game 21-16.
The twists and turns did not stop there.
This time Chen was slow out of the blocks and trailed 11-6 but a key exchange with coach Xia Xuanze at the mid-game break saw her return a new player and she subsequently won six straight points and nine out of the next 11 to go up 15-13.
Post-match she said: “I felt I played a bit slow at the beginning of the third game which caused me to waste a lot of energy. I couldn’t keep up with her but at the break I changed my game strategy and I took the lead.”
Yamaguchi continued to fight but with the home crowd on her side, Chen pulled away to record a famous victory.
Japan coach Park Joo Bong acknowledged later: “Yamaguchi was leading 11-6 in the third game but she could not continue her good rhythm. That was a very big mistake.”
Yamaguchi herself said: “I fell into playing at Chen’s pace and not my own pace and rhythm and that’s why I lost the advantage.”
The loss would give her countryman Kento Momota a mountain too high to climb.
There’s no doubting the Chen-Yamaguchi rivalry will last for many years to come. It currently stands at 9-6 in favour of the Japanese, but you can’t help to think that Chen is slowly getting the upper hand.