With both players having beaten No.8 seed Donna Vekic in straight sets this week already, the final round-robin match of the Azalea Group was a winner-takes-all tilt. Dealing expertly with her teenage opponent's pace, it was Bertens who came out on top, with her Zhuhai campaign having now precisely duplicated the start of her run to the Beijing semifinals, which saw the Dutchwoman defeat Vekic and Yastremska in the first two rounds.
That experience, Bertens said, had helped her today strategically. "Changing the rhythm, I think that's what she doesn't like," she remarked of her opponent. "She really likes that every ball is coming at the same height, at the same pace. So just throwing in some slices, I think she's really struggling with that - I saw that already in Beijing and I think today again. So I think that's what I normally do already, but I think that against players like Dayana, even more."
Bertens, who has played every week since the US Open across two continents, also said she was "just really proud and happy" at how she has held up physically so far in Zhuhai - though also somewhat surprised. "I feel like my body's falling apart," she laughed. "But I think every match I'm just like, OK, maybe this is your last match of the season - so just give everything, and that's what I did."
Yastremska struggled on serve in the opening stages, committing four double faults in her first three service games - a passage of play that saw her get broken twice and which left her playing catch-up throughout the set. The Ukrainian also had her share of dazzling highlight-reel points - a reflexed backhand volley paved the way to getting one of the breaks back, and allying her trademark fierce forehands to canny use of the slice and a winning dropshot helped to level the score at 4-4 - but Bertens' ability to maintain the scoreboard pressure proved crucial.
The St Petersburg and Madrid champion, playing from far behind the baseline, demonstrated the strength, consistency and anticipation needed to patiently soak up all of Yastremska's pace. Doggedly getting everything she could back in court, Bertens was eventually able to draw the error even in the longer rallies that found the 19-year-old displaying more patience than usual - and despite the Yastremska fightback, this strategy would pay off as Bertens ground out four straight games, breaking twice to take the first set and move up 2-0 in the second.
Yastremska continued to compete valiantly, making inroads into Bertens' serve throughout the remainder of the set with more stunning winners - including a pair of excellent volleys that earned her a break-back point in the eighth game.
The World No.10, though, was simply too solid. Able to call on her formidable serve to back up her tenacious defence, Bertens extricated herself from the potential turning point with a brace of service winners, before breaking again for the win as a frustrated Yastremska's forehand broke down and the youngster committed a fifth double fault down match point.