Andy Roddick bowed out of the SAP Open at the quarter-final stage, losing to Denis Istomin.
The former world number one, trying to find his form again after an injury-ravaged start to the season, bowed out 6-2 6-4.
He was clearly rattled, too, hitting balls out of the court, breaking his rackets, arguing with the umpire and shouting at his coaching box.
His demeanour was somewhat different to that of the latest American star, teenager Ryan Harrison.
He cruised through his last-eight tie with Dimitar Kutrovsky, winning 6-1 6-4 to move to within two wins of what would be a first ATP title.
He needs to beat the defending champion to reach the final, though, with big-serving Milos Raonic having got the better of Kevin Anderson 7-5 7-6 (7/3) to set up a semi-final meeting.
In the day's final match, Julien Benneteau came from behind to defeat Steve Darcis 3-6 6-1 6-2, setting up a meeting with Istomin in the semi-finals.
