The defending champion and top seed at the Dubai Duty Free Tennis Championships, Elina Svitolina, needed only an hour and 22 minutes to beat the Japanese star, Naomi Osaka, 6-2, 6-4, and confirm her place in the semi-finals of the Premier 5 tournament.
Number one seed Svitolina eased past former world number one Angelique Kerber 6-3, 6-3.
Russia's unseeded Kasatkina saved three match points before going on to upset Wimbledon champion Muguruza 3-6 7-6 (13-11) 6-1 in a match lasting two-and-a-half hours. Up next for Muguruza will be the victor of the match between Russia's Daria Kasatkina and Ukraine's Elena Vesnina.
Kerber ended 2017 at No.21, making one final in Monterrey and two semifinals in Dubai and Tokyo, but the key to past year lay in the fact that she stuck with it, pushing, trying to find a way.
"I didn't expect (to play three sets), but I always try to expect the unexpected", Svitolina said postmatch.
Muguruza, seeded to meet holder Elina Svitolina in the final, said she is less stressed by her ranking now that she's been to the top and back.More news: Honda Classic: Tiger Woods under par through first nine holes
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"When you're winning from match points (down), you don't know why", she said. "I was trying to play good returns back, then just play my game". She's hitting so hard, playing so fast. "I'm going to deserve be just laying down at some hotel, swimming pool". Nonetheless, the Spaniard found her groove soon, displaying some top-notch tennis despite having a tinge of inconsistency in her game.
Sixth-seeded Angelique Kerber of Germany ousted 2016 champion Sara Errani of Italy 6-4, 6-2, while No. 5 Caroline Garcia of France won by an identical score over Ekaterina Makarova of Russian Federation.
"It should be a good final, Daria is playing well, and she's won some tough matches".
"For sure. I think those are the important wins in the season, not when you play the best tennis".
"I'm really happy to have won this match", Vesnina said. I think she has a good fitness to be able to run a lot.
"Yeah, definitely I'm happy the way I've been handling the pressure and tough moments".