Milan - Top seed Andrey Rublev reached the ATP NextGen semi-finals on Thursday, edging out Canadian shot-maker and third seed Denis Shapovalov 4-1, 3-4 (8/10), 4-3 (7/2), 0-4, 4-3 (7/3).
Russian star Rublev became the third semi-finalist of the inaugural tournament after Hyeon Chung of South Korea and Croatia's Borna Coric.
Later Thursday, Karen Khachanov's hopes of squeezing into the last four ended when Coric battled to a 3-4, 2-4, 4-2, 4-0, 4-2 win.
Khachanov's defeat means that Russian compatriot Daniil Medvedev, who earlier defeated Jared Donaldson in four sets, will make up the semi-final line-up.
"It was a really, really tough match," world number 37 Rublev said. "I'm really happy that in the end I made it."
Thursday was a first career meeting for Rublev and Shapovalov and the Russian is confident that there will be many more.
"I hope so. I hope I will be at a good level to fight with all the guys, with Denis, with all the other guys," Rublev told atpworldtour.com.
In Friday's semi-finals, Chung tackles Medvedev while Coric meets Rublev.
Results from the third day of the Next Gen ATP finals under-21 tournament in Milan on Thursday:
Hyeon Chung (KOR) bt Gianluigi Quinzi (ITA) 1-4, 4-1, 4-2, 3-4, 4-3
Andrey Rublev (RUS) bt Denis Shapovalov (CAN) 4-1, 3-4, 4-3, 0-4, 4-3
Daniil Medvedev (RUS) bt Jared Donaldson (USA) 3-4, 4-2, 4-3, 4-0
Borna Coric (CRO) bt Karen Khachanov (RUS) 3-4, 2-4, 4-2 4-0 4-2.
Friday's semi-finals (x denotes seeding)
Hyeon Chung (KOR x6) v Daniil Medvedev (RUS x7)
Borna Coric (CRO x4) v Andrey Rublev (RUS x1)