Marin Cilic gained revenge for defeat in the final of the 2010 BMW Open with a 6-3 6-7 (6-8) 6-3 quarter-final win over Mikhail Youzhny.
Youzhny saved a match point in the second set tie-break and then went on to take control of the decider with an early break.
But Cilic rallied to break Youzhny's service twice in the final set to win in two hours and 45 minutes.
"In the second set, Misha was playing unbelievable," Cilic told the ATP World Tour's official website. "He saved a match point with an amazing backhand down the line. "What I was happy about today was that I kept my level going. Even though I lost my serve at the beginning of the third set, I got the momentum back and I think that was really crucial."
In beating the Russian, Cilic earned himself a semi-final meeting with home favourite Tommy Haas who beat Marcos Baghdatis 6-1 7-6 (7/3).
Haas, only playing on a wild card, had seen off top seed Jo-Wilfried Tsonga in the previous round.
On the other side of the draw, Feliciano Lopez defeated Bernard Tomic 6-4 6-2 to set up a meeting with Philipp Kohlschreiber. The German beat Marinko Matosevic 6-0 7-6 (7/5).
