Sydney: 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 semi-finals.
Seppi, 14 years older than his 20-year-old Greek opponent, has only won three ATP titles in his career, but called on all his experience as he battled back for a gutsy 4-6, 6-4, 6-4 win.
"For some reason I always play my best tennis in Australia, so I really enjoy being here," said Seppi, who broke immediately in the second set after losing the first.
"It was very important to start well in the second set. Good to have an early break so I could play a bit more aggressive and it worked out in the end."
Australia has been a home away from home for the Italian in recent years.
In a trio of round-of-16 appearances at the Australian Open, he pulled off upsets against Marin Cilic in 2013, Roger Federer in 2015 and Nick Kyrgios in 2017.
Defeat was a blow for world No 15 Tsitsipas' preparations for the opening Grand Slam of the year in Melbourne next week.
He was one of the sport's most improved players last year, climbing from 91 after reaching finals in Barcelona and Toronto, losing both to Rafael Nadal, and was angling for the perfect start ahead of the Australian Open.
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 quarter-final 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.
The 22-year-old is now on a six-match win streak, dating back to her career's biggest title at the WTA Elite Trophy in Zhuhai.
"Nice and solid today, I was pretty happy at the way I was able to come out and play," said Barty, ranked 15 in the world. She will play either seventh seed Kiki Bertens or Yulia Putintseva, who beat Sloane Stephens in round two, for a place in the final.
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.
But she has a daunting task ahead, playing either world number two and defending champion Angelique Kerber or fifth seed and 2015 Sydney winner Petra Kvitova, who meet in a match headlining Thursday's night session.
In 12 meetings on tour, Kerber and Kvitova have won six each and split their two meetings in 2018.