SINGAPORE -(AFP) - Poland’s Agnieszka Radwanska overpowered Karolina Pliskova 7-5 6-3 on Friday to clinch the last available place

in the semifinals of the WTA tour championship and stay on course to defend the title she won last year.
Radwanksa made a stunning comeback to win the 2015 tournament despite losing her first two round-robin matches and made it through to the last four again after having lost her opening match by beating the big-serving Pliskova in a sudden-death showdown.
“I think that was simple,” Radwanska said. “You win, you’re still there. You lose, you’re out. Not much math here.
“I definitely knew I had to play my best tennis against her. She was showing only good tennis this week as well.”
The 27-year-old Pole will now face her good friend, world number one Angelique Kerber, in Saturday’s semis with the winner to play either Russia’s Svetlana Kuznetsova or Dominika Cibulkova of Slovakia.
Kuznetsova suffered her first loss of the tournament on Friday when she was beaten 3-6 6-0 6-1 by Spain’s French Open champion Garbine Muguruza but the result had no bearing on the semis with the Russian already assured of finishing top of the White Group and Muguruza out of contention after losing her first two matches.
“I have to be honest, going into this match was extremely hard for me,” Muguruza said.
“At the end, my desire of wanting to be here and competing against the best, was a challenge for me today to see how I was going to react.
“I’m very happy with the way I played today, the way I handled the match. A victory like today is going to keep me a little bit happier. It was a very tough tournament.”
Pliskova, who qualified for the elite end-of-season event when she reached the final of the US Open last month, led 4-2 in the opening set and was also a break up in the second before the more experienced Radwanska took control on the key points.
Radwanksa has never lost to Pliskova in seven meetings and she capitalized on the Czech’s 29 unforced errors, which included hitting two routine overheads into the net late in the second set.
“In this tournament, with the best eight players, you see that every match is close. It’s just decided by a few balls,” Pliskova said.
“She also knew she has to win. She always beats me, so I just believed that she might miss in the close moments a little bit but she didn’t. I think she just controlled the whole match.”
Kuznetsova finally ran out of steam after winning a tournament in Moscow last weekend just to qualify for the WTA Finals then winning two gruelling matches at Singapore’s Indoor Stadium.
The 31-year-old seemed to be in cruise control after she took the opening set against Muguruza but won just one game in the last two sets as the physical effects of the past week began to take a toll.
“I’ve done the most important job in the past matches,” Kuznetsova said. “You definitely don’t want to lose the match. You try to fight (but) sometimes the lack of energy just won’t let you do that.”