The final four, the final two, and a huge upset

🇷🇴 Semis for Simo 🇷🇴#AO2020 | #AusOpen | @Simona_Halep pic.twitter.com/Tn08I4fw4Y

— #AusOpen (@AustralianOpen) January 29, 2020

They represent Australia, the USA, Romania, and Spain. Three of them have won majors, though none of them has ever won the Australian Open. None, in fact, has ever won a hard court major. Ash Barty, Sofia Kenin, Simona Halep, and Garbine Muguruza (who is unseeded) will compete tomorrow to determine who goes to the finals in Melbourne.

Barty, backed by thousands of adoring Australians, defeated 2019 runner-up Petra Kvitova in straight sets in the first day of quarterfinal play. The first set was extremely competitive, with both players in top form. But in the second set, Kvitova began to fade. It could have been mental, physical, or both, but it was most likely physical. It was kind of sad to watch, though those of us who follow the Czech star are aware that this kind of thing can happen at any time, and especially in a hot climate.

Barty, for her part, was steady and--even in the first set--able to keep up with a barrage of "Peak Petra" groundstrokes. In the semifinals, she'll play Kenin, who defeated Ons Jabeur, also won in straight sets.

In yesterday's first quarterfinal, Halep handily defeated Anett Kontaveit 6-1, 6-1 in just 53 minutes. In the second match, Muguruza defeated Anastasia Pavlyuchenkova 7-5, 6-3. It's notable that Muguruza was quite ill during her first match. She lost the first set 0-6 and had to have her blood pressure checked. It would have been a real shame if she had not overcome the illness.

Muguruza will play Halep for a spot in the final, and this may be as good as it gets in terms of tennis excitement.  The two have played each other six times. One of the matches resulted in a walkover, and, of the remaining, Muguruza is 3-2 against Halep. All three of the Spanish star's victories were on hard courts (Cincinnati, Fed Cup, Wuhan).

In doubles, seeds 1 and 2 are the last two teams standing. Top seeds Hsieh Su-wei and Barbora Strycova defeated 4th seeds Barbora Krejcikova and Katerina Siniakova 6-2, 6-3, and 2nd seeds Timea Babos and Kiki Moadenovic defeated 7th seeds Chan Hao-Ching and Latisha Chan 7-5, 6-2. Babos and Mladenovic won the Australian Open in 2018 and were the runners-up last year.

🚨 Upset Alert 🚨

China's first-ever wheelchair player to compete at a Grand Slam, Zhu Zhenzhen, knocks out No.1 seed and two-time #AusOpen champion Diede De Groot, 6-7(3) 6-3 7-5 to reach the #AO2020 semifinals. pic.twitter.com/XJbYn1YVdH

— #AusOpen (@AustralianOpen) January 29, 2020

One of the biggest upsets of this year's Australian Open occurred yesterday in the quarterfinals of wheelchair singles when Zhenzhen Zhu, the first woman from China to compete in a wheelchair major, defeated defending champion Diede De Groot. De Groot saved eight match points, but even that wasn't enough; Zhu prevailed, 6-7, 6-3, 7-5. It was an enthralling match. De Groot's defense was outstanding, but in the final set, her usually reliable serve failed her at times.

The Dutch wheelchair star won the tournament in both 2018 and 2019. Diede De Great, as she is known, was one tournament shy of winning the Grand Slam last year. She has won seven majors in singles and eight in doubles.