Kvitova topples Kerber to reach semis

Veteran Andreas Seppi on Thursday derailed top seed Stefanos Tsitsipas' Sydney International title hopes, while homegrown rising star Ashleigh Barty claimed another top scalp to also make the semifinals.

Seppi but called on all his experience as he battled back for a gutsy 4-6, 6-4, 6-4 win.

Seppi's reward is a clash with third seeded Argentine Diego Schwartzman, who needed to fight hard to beat Japanese qualifier Yoshihito Nishioka 6-1, 3-6, 7-6 (7/1).

In other quarterfinal action, fifth seeded Alex De Minaur takes on fellow Australian Jordan Thompson while France's fourth seed Gilles Simon faces another Australian, John Millman.

Australia's Barty followed up her giant-killing wins over world number one Simona Halep and former French Open champion Jelena Ostapenko by easily accounting for 10th seeded Belgian Elise Mertens 6-3, 6-3. Barty will next face Czech Petra Kvitova.

Kvitova overcame rain delays to beat defending champion Angelique Kerber 6-4, 6-1 on Thursday and reach the semifinals.

In wet conditions at Ken Rosewall Arena, Kvitova struggled to get going but took the final four games of the opening set, hitting 16 winners in the process.

The 22-year-old Barty is now on a six-match win streak, dating back to her career's biggest title at the WTA Elite Trophy in Zhuhai.

The first woman to book a semi spot was Belarusian qualifier Aliaksandra Sasnovich, who beat Switzerland's Timea Bacsinszky -- on the comeback trail after a 14-month winless spell -- 6-3, 6-3.

Cilic through

Meanwhile, last year's Australian Open finalist Marin Cilic rounded off his preparations for this year's edition in style on Thursday, winning his second match in as many days at the Kooyong Classic.

The world number seven beat Spain's Fernando Verdasco 6-4, 6-4, backing up his three-set victory a day before over world No 6 Kevin Anderson.

Earlier, American Jack Sock lost to fast-rising Canadian teenager Denis Shapovalov 6-2, 3-6, 10-7 after a final set played as a 10-point tiebreak -- the format which will be used at the Australian Open from Monday.

Shapovalov, 19, made up for lost time after losing in the first round at Auckland this week and then crossing the Tasman to squeeze into the Kooyong draw as a late entry.

Fognini ousted

In Wellington, Evergreen Philipp Kohlschreiber rolled back the years to storm into the Auckland Classic semifinals on Thursday with a straight-sets demolition of second seed Fabio Fognini.

The 35-year-old German tore apart the lacklustre Italian 6-3, 6-1.

Currently ranked 34th in the world, Kohlschreiber has not dropped a set on his way to a final four showdown with American Tennys Sandgren, who beat Argentina's Leonardo Mayer 6-3, 7-6 (7/5).

The other semi-final pits Briton Cameron Norrie -- a victor over American Tyler Fritz -- against Jan-Lennard Struff of Germany.