Matteo Berrettini came back from a set down to beat Nikoloz Basilashvlili 6-7 (5-7), 6-3 6-2 at the Erste Bank in Vienna in a tense match that lasted two hours and five minutes.
Berrettini had never lost to Basilashvlili and his form continued as he fired 22 aces on his way to victory over the Georgian, who won the first first set after a tiebreak.
The Italian opened up a 3-0 lead and held his next service games to take the set before going 3-0 up in third.
Berrettini faced a break point in the seventh game, but saved it with an ace and then served out the match.
He will face Spanish teenager Carlos Alcaraz, who beat Andy Murray 6-3 6-4, next.