Feliciano Lopez hammered 19 aces and saved all nine break points faced as the Spaniard knocked third seed Tomas Berdych out of the quarter-finals of the Mercedes Cup 6-7 (4-7), 6-3, 6-4 on Friday.
The Czech dropped to 6-7 in the series with one of the few Spaniards who is quite content to play on grass.
Number 14 Berdych joined seeds Roger Federer and Grigor Dimtrov in making an exit.
The 33rd-ranked Lopez awaits his semi-final opponent as Federer’s conqueror Tommy Haas faces fellow German and sixth seed Mischa Zverev.
Lopez, 35, staged a fighting comeback after losing the opening set in a tiebreaker and eventually prevailed to take his season record to 12-12.
French fourth seed Lucas Pouille held off a fightback attempt from German Philipp Kohlschreiber to earn a 6-4, 2-6, 6-3 trip to the final four. Kohlschreiber finished runner-up in 2013 and a year ago against Dominic Thiem.