Agnieszka Radwanska believes she has a 50-50 chance of coming out on top in her WTA Finals last-four clash with world number one Angelique Kerber on Saturday.

Defending champion Radwanska booked her placed in the semi-finals by defeating Karolina Pliskova 7-5 6-3 on Friday, her seventh win in as many matches against the Czech.

The Pole believes there will be more pressure on Kerber, who trails 6-5 in their head-to-head record, but that either can player come out on top in the meeting of the top two-ranked players remaining in Singapore.

"I think here, of course she's number one, but it's 50-50. There's just eight of us [at the start of the tournament] and it's the semi-finals, so everyone has the same chance," said Radwanska.

"She probably has more pressure after her season and being number one, but everyone can go through and everything is open in the semi-finals.

"We didn't play this year so it's exciting, especially after the year she had. It'll be a good challenge for me and I hope I can keep it going."

Pliskova failed to convert a break point to go 5-2 up in the first set and did the same at 3-3 in the second, but the Czech tried to stay positive despite her missed opportunities.

"In the first set I didn't do anything bad, I was up 4-2, 30-0 [up] and she played a really good game at that time," she said. 

"She served really well and I missed four break points. She didn't [miss] and I think she just controlled the whole match.

"I will take it as a good step that I even got here and I was able to win my first match [at the WTA Finals, against Garbine Muguruza]. I think I played some good matches, some good tennis.

"I'll be more experienced next year and hopefully I'll be back."