Top-seeded Janko Tipsarevic of Serbia had to save four match points before finally overcoming Bjorn Phau of Germany 6-7 (6), 7-6 (2), 6-4 on Friday to reach the semifinals of the Mercedes Cup.
Second-seeded Juan Monaco of Argentina beat qualifier Pavol Cervenak of Slovakia, 6-1, 7-5 and will next meet Guillermo Garcia-Lopez of Spain, who defeated Dustin Brown of Germany 6-0, 6-3.
Tipsarevic failed to convert 10 break points in the seventh game, and then let four set points slip away in the tiebreaker as Phau closed out the set with six straight points.
Phau broke for 6-5 in the second but could not convert four match points and Tipsarevic then cruised through the tiebreaker.
Tipsarevic saved four break points before serving out the match.