David Goffin led 3-6 and 2-5, inheriting a match point. The Belgian was then able to serve for the match at 3-5, but conceded 5 games in a row which allowed his opponent to return to the game.
Goffin then only pocketed two games in the 3rd set to leave the tournament after having passed the milestone of two qualifying matches.
Jiri Lehecka, 22, won his first ATP title in Adelaide, Australia a month ago and had already climbed to 23rd in the world.
The Pole Hubert Hurkacz, seeded N.1, is the defending champion. In 2019, Goffin reached the semi-finals and lost to the future winner, the Greek Stefanos Tsitsipas.