American Steve Johnson accounted for second seed Kevin Anderson in Friday's Erste Bank Open quarter-finals in Vienna.
Johnson also had the edge over the South African in their only previous encounter, and followed that up with a 5-7 7-6 (7-5) 6-4 victory after a marathon two hours and 40 minutes.
Johnson moves on to face Latvian Ernests Gulbis, who continued his recent resurgence by powering into the semi-finals with a hard-fought 7-6 (7-4) 7-6 (7-5) victory over Ivo Karlovic.
Gulbis fended off 19 aces and saved all five break points him.
The other semi-final will see top seed David Ferrer take on France's Gael Monfils.
Ferrer claimed a pretty straightforward 6-4 6-2 victory over eighth seed Fabio Fognini – his ninth consecutive positive result against the Italian.
Ferrer will significantly strengthen his bid to secure qualification for the ATP World Tour Finals if wins Saturday's semi-final.
Monfils, meanwhile, dropped the first set against Lukas Rosol but hit back strongly to secure a 6-7 (3-7) 6-3 6-3.