Home favourite Aslan Karatsev had to save four set points on his way to a 6-4, 6-3 win over Gilles Simon at the Kremlin Cup in Moscow on Friday.
Karatsev, who has not dropped a set all week at the event, broke Simon five times in the match and will face Karen Khachanov next.
Khachanov beat Aussie John Millman 7-5, 7-6 (7-5) in lengthy see-saw battle that lasted two hours and 26 minutes.
Khachanov took a 4-3 lead only for Millman to break back to draw level to 4-4.
The Russian then grabbed a second break to take the set.
In the second set Khachanov opened up a 5-1 lead before Millman pulled it back to 3-5, but Khachanov then closed out the tie with a break on match point.
Emma Raducanu and Katie Boulter hit the exits on Friday at the Madrid Masters, with…
Alexander Zverev maintained his clay court momentum from this month;s Munich title, with the German advancing in…
Novak Djokovic agreed on Thursday that players can be "slaves" to tennis, after complaints by Carlos…
Carlos Alcaraz was forced to withdraw from the Madrid Masters on Thursday with a pair…
Emma Raducanu ended a month-long break from tennis to pick up her first clay win…
Belinda Bencic began the Madrid Masters with a win while three-time tournament winner Petra Kvitova was…