Antwerp - Italian teenager Jannik Sinner became the youngest ATP semi-finalist in five years on Friday when he defeated Frances Tiafoe of the United States 6-4, 3-6, 6-3 to make the last four of the European Open in Antwerp.
Sinner, 18, is the youngest to make the last four on tour since 17-year-old Borna Coric at Basel in 2014.
"I think I played good today once more. It was not easy in the end. I was shaking a little bit," said Sinner, the world No 119.
The teenager fired 10 aces past the 53rd-ranked Tiafoe, saving four of five break points as he backed up his defeat of French top seed Gael Monfils in the second round.
Sinner, who was ranked 778 this time last year, can make the world top 100 next week.
However, he faces a daunting semi-final against three-time major winner Stan Wawrinka after the former world No 3 got past fellow 34-year-old Gilles Simon of France 6-3, 6-7 (6/8), 6-2 in his quarter-final.
Sinner, who lost to Wawrinka at the US Open this year, will become the youngest ATP finalist since Kei Nishikori at Delray Beach in 2008 if he downs the experienced Swiss on Saturday.
Later Friday, former world No 1 Andy Murray faces Romanian qualifier Marius Copil in his quarter-final while Argentine fifth seed Guido Pella tackles Ugo Humbert of France.
Murray, ranked a lowly 247 as he battles his way back from hip surgery, is bidding to reach a first tour-level semi-final since Roland Garros in 2017.