Top seed Agnieszka Radwanska powered into the semi-finals of the Connecticut Open, after two-time defending champion Petra Kvitova made it past the last eight.

Radwanska made light work of Kirsten Flipkens in straight sets at the WTA Premier event in New Haven on Thursday, while sixth seed Kvitova dispatched Ekaterina Makarova in two to set up a mouth-watering semi.

Roberta Vinci - the second seed - was not so fortunate, stunned by Johanna Larsson, who will face Elina Svitolina in the final four following the 10th seed's victory over Elena Vesnina.

FIRST CONNECTICUT SEMI FOR RADWANSKA

Former world number two Radwanska saw off Flipkens 6-1 6-4 to earn a maiden semi-final berth in New Haven.

Radwanska - boasting a 34-13 win-loss record this season - lost to Kvitova in the quarter-finals last year but the Pole was not denied this time around.

Despite only serving at 42 per cent through the one hour, 22-minute contest, Radwanska was far too strong as she converted five break points, while fending off six of her own.

THREE-PEAT LOOMING FOR KVITOVA

The Kvitova train continues to roll on at the Connecticut Open after the Czech eased past Makarova 6-3 6-1.

Two-time grand-slam winner Kvitova needed just one hour on court to reach the semi-finals of the tournament for the fifth year in a row.

Attempting to match the feats of Caroline Wozniacki and Venus Williams, who won three successive titles in New Haven before going on to claim four on the trot, 2012 champion Kvitova was not broken in the match, capitalising on four of her own.

LARSSON IGNORES THE SCRIPT

Italy's second seed Vinci was supposed to advance to the semis, well at least that was the plan, but lucky loser Larsson had other ideas.

In a big upset, Larsson - who failed to make it past the qualifying rounds last year - overcame Vinci 7-6 (11-9) 6-1 in the quarter-finals.

Almost throwing away the opening set, having brought up two set points at 5-4, Larsson eventually held off Vinci in the tie-break to edge ahead in the match.

The Swede continued where she left off in the second, breaking four times as she reeled off five successive games to secure a showdown with Svitolina, who cruised to a 6-3 6-1 victory against Vesnina.

KVITOVA FEELS AT HOME IN NEW HAVEN, VINCI BEMOANS INJURY

Winner of three Connecticut Open titles as she prepares to battle Radwanska for a spot in decider, Kvitova said: "It's always nice coming somewhere when you feel, you know, at home and you know you can play well. It always gives you a little bit more confidence than normally."

Following her shock defeat, Vinci told reporters: "I'm injured a little bit. I have a little bit of pain of my tendon on left foot. On the second set, I was not tired. But I thinking always about my pain, and I lost. But now I have two or three days off before New York to try to recover and stay better for the US Open."

WHO WILL REACH DECIDER?

Friday will see Svitolina and Larsson kick-off the semi-final schedule, before Radwanska and Kvitova meet in the evening session.