The 2021 Viking Classic will see either No.2 seed Ons Jabeur lift her maiden WTA trophy or No.4 seed Daria Kasatkina win her third title of the year after the pair emerged victorious from an action-packed day in Birmingham.

Rain had washed out the whole of Friday's play, necessitating all four quarterfinals and both semifinals to be played on Saturday. Mindful of her task, Jabeur delivered two supremely focused performances to defeat Anastasia Potapova 6-4, 6-0 in 56 minutes and then Heather Watson 6-3, 6-3 in 72 minutes.

Kasatkina was not quite as efficient but still sharp in getting past two qualifiers - Tereza Martincova 6-4, 2-6, 6-0 in one hour and 44 minutes, followed by CoCo Vandeweghe 6-2, 6-4 in one hour and 16 minutes.

"I tried not to waste my time on court, to keep my energy for a long day," said Jabeur.

Against Potapova, Jabeur reeled off 11 out of 12 games from 1-3 down in the first set, smothering the 20-year-old Russian with precise shotmaking. Against Watson, she dropped just three points on serve in the first set, finished with 17 winners to 12 unforced errors and fired six aces.

Watson had earlier upset No.3 seed Donna Vekic 6-4, 6-2 to become just the third Briton to reach the last four in Birmingham in the tournament's 31-year history, following Anne Hobbs in 1984 and Jo Durie in 1992. Her run was also a much-needed turnaround in her fortunes. Watson came into the week sporting a 4-10 record in 2021, and 6-16 since the tour resumption last August.

The World No.70 intermittently impressed against Jabeur, particularly in giving the Tunisian a taste of her own medicine with several stellar dropshots. One of those garnered Watson the only break of Jabeur's serve, at the start of the second set.

But Watson was hindered by four double faults, one in each of her service games in the first set, and an occasional sprinkling of several cheap errors in a row.

Brilliant Kasatkina bests Martincova to make first grass SF: Birmingham Highlights

Kasatkina's quarterfinal triumph over Martincova was the highest-quality match of the day, particularly during a deciding set in which she out-manoeuvred the rising Czech in a sequence of thrilling extended exchanges.

Her semifinal against Vandeweghe was a markedly different proposition. The former World No.9 is still on the comeback trail after being sidelined due to complex regional pain syndrome in 2019, and then hand surgery after a freak microwave accident in 2020.

Both of Vandeweghe's career titles have come on grass, in 's-Hertogenbosch in 2014 and 2016, and her power game was clicking as she stormed past Marie Bouzkova 6-4, 6-4 in the last eight. The result was the American's first Top 50 win since beating Caroline Garcia in the 2018 Stuttgart semifinals, and put her into the last four of a WTA tournament for the first time since 's-Hertogenbosch 2018.

Vandeweghe bookended her match against Kasatkina with similar form. Blitzing winners and racing to the net at every opportunity, she led 2-1 after a pulsating opening three games. A last-ditch comeback saw her recover that level to win four of the last six games.

But in between, once Kasatkina had become accustomed to her opponent's power and started moving the ball around more effectively, Vandeweghe's radar went awry. From 2-1 up, she lost nine straight games, including 28 out of 37 points.

Most shots she attempted ended up in the net or outside the lines. Vandeweghe finished with 30 unforced errors to 14 winners, and only landed 50% of her first serves.

Kasatkina nearly paid the price for becoming too passive in the face of Vandeweghe gifts, but managed to serve out the win at the second time of asking after a final pair of forehand errors from the World No.203.

"The goal was just to handle as much as I can and resist this aggressive game," Kasatkina said afterwards. "I'm happy that I was able to close the match. It was a busy day in a great office!"

The result moves Kasatkina into her eighth career final, first on grass and third of 2021 already following titles at the Phillip Island Trophy and St. Petersburg. For Jabeur, it will be a third final and second of the season after falling at the MUSC Health Women's Open to Astra Sharma. Jabeur's biggest title to date was a grass-court event, the 2018 Manchester ITF W100.

Tomorrow's clash will also be a rematch of the 2018 Moscow final, which Kasatkina won 2-6, 7-6(3), 6-4 after trailing 2-6, 1-4.

"The last time we played a final, it was a big, big drama!" she recalled.

It was also a match of high quality between two of the tour's most talented improvisers and shotmakers - something that fans can look forward to being enhanced on grass in Sunday's final.