Jannik Sinner doubled up on his defeats of Alex De Miinaur on Thursday, with the Italian teenager knocking the Australian out in the quarter-finals of the ATP event in Sofia

Sinner, 19, rallied from a set down against the 21-year-old “Demon,” whom he defeated a year ago this week for the NextGen title in Milan.

Sinner sailed into the Sofia semi-finals 6-7(3), 6-4, 6-1, taking just over two hours to advance; he also reached the final four last month in Cologne..

The winner saved six of the seven break points he faced while breaking De Minaur five times.

He will play on Friday against Frenchman Adrian Mannarino, a winner over Radu Albot 6-2, 1-6, 6-3.

The semi-final will be a first-time meeting.

“(He’s) a tough player, a lefty who is serving well and moving well in long rallies,” Sinner said of Mannarino, 32..

“It’s going to be a physical match. I’ll need to speak with my coach about to prepare for tomorrow.

The 44th-ranked Sinner stands 17-11 this season; Mannarino lost the Nur-Sultan final in Kazakhstan early in the month to Aussie John Millman.