Zhengzhou, China, 14 September 2019 | Reuters / tennis.com.au

Ajla Tomljanovic battled to a three-set victory over home favourite Saisai Zhang at the Zhengzhou Open on Friday to set up a testing semifinal clash with world No.2 Karolina Pliskova.

Australian No.2 Tomljanovic, who claimed the biggest win of her season with a straight-sets victory over world No.8 Kiki Bertens earlier in the day, ensured her passage to the last four with a 6-1 6-7(4) 6-4 over Zhang, ranked eight places above her at No.38.

It marks her third semifinal of the season — she reached the same stage in Hua Hin and Rabat, advancing to the final at the former — and first at WTA Premier-level.

Tomljanovic also played her doubles quarterfinal with Alicja Rosolska, falling 2-6 6-0 [10-5] to top seeds Nicole Melichar and Kveta Peschke.

“I’m exhausted,” Tomljanovic laughed.

“At the start of the day, I told myself if I play three matches today, I’ll be happy, because at least I probably won one of my singles, but two out of three for now … so I’m really pleased I’m in the semis.”

The Australian led Zheng 6-1 3-1 before the Chinese star stormed back, but Tomljanovic re-focused in the third set, recovering from an early break down to win after two hours and 35 minutes.

With her match against Bertens finishing just shy of two hours and her doubles match lasting almost an hour, Tomljanovic spent approximately five-and-a-half hours on court on Friday.

“Honestly I hate playing Saisai, she just makes me work so hard for it. I think her game doesn’t suit me so much so I always have to I feel like work a little bit extra hard,” Tomljanovic admitted.

“She definitely made me work today; I’m kind of upset I didn’t take advantage of that 6-1 3-1 lead but I kind of expected it, that it would go three sets (laughter).

“I feel I came into the Saisai match a little more relaxed than I would have if I didn’t play Kiki two hours before, so I think it helped. But obviously I wish it wasn’t three matches in a day (smiling).”

She now faces top seed Pliskova, who started Friday in the last-16 and ended the day in the semis after defeating Polona Hercog and Sofia Kenin in succession.

“I think it’s pretty straight forward (against Pliskova). She has a big game, big serve, plays big from the back,” Tomljanovic said.

“I definitely know we won’t be on the court for too long — I think one time our two sets were under like 50 minutes in Brisbane, so I’m happy about that (laughter). But I’m definitely going to have to be sharp from the first ball tomorrow.”

Pliskova’s match against Slovenian Hercog was suspended on Wednesday due to rain with the score at 6-3 2-5 and she only returned to court two days later after rain washed out Thursday’s matches.

The Czech claimed five games in a row to see off Hercog 6-3 7-5 and carried that form into her quarter-final clash with sixth-seeded American Kenin, winning 6-4 4-6 6-1.

“To play two matches in a day, it’s never easy,” said the Czech, who saved nine break points, including six in the final set.

“I also played Tomljanovic in Rome, and in Brisbane on hard courts, so I know her game quite well, I could say.

“She’s dangerous and beat Kiki Bertens, so she’s playing well. I didn’t see much of her tennis here but it’s the semifinals, so everyone is confident and playing their best tennis.”

The upset of the day saw France’s unseeded Kristina Mladenovic beat second seed and new world No.3 Elina Svitolina 6-4 4-6 6-3 in the final match of the day that lasted two hours and 45 minutes.

Mladenovic will now face Croatia’s Petra Martic, who earlier beat fourth seed Aryna Sabalenka 7-5 5-7 6-4 in another lengthy encounter that lasted two hours and 39 minutes.