British No 2 Dan Evans beat Michael Berrer to book his place in the quarter-finals of the PBZ Zagreb Indoors.
Evans, who had lost in qualifying before being added to the main draw on a withdrawal, won his second match of the week defeating the German qualifier 1-6 6-1 7-6.
The world No 147 struggled in the first set, making only 33 per cent of first serves as his opponent took the two break points that came his way.
But the 23-year-old turned the match around in the second, breaking twice himself.
Indeed, he did not face a single break point in either of the last two sets, wasting three break chances in the third before taking it 7-4 on a tie-break.
He will play third-seeded German Philipp Kohlschreiber in the last eight after he saw off Andrey Golubev of Kazakhstan 6-4 6-2.
German Bjorn Phau, who beat Evans in qualifying, continued his great week by ousting second seed Mikhail Youzhny of Russia 4-6 7-5 6-1.
Meanwhile, Israeli Dudi Sela brushed Slovakian Lukas Lacko aside 6-3 6-2 and fourth seed Ivan Dodig beat Ivo Karlovic 7-6 6-3.
Top seed Tommy Haas surprisingly dropped the first set before battling past fellow German Benjamin Becker 4-6 6-3 6-3.