Andy Roddick revealed his growing frustrations with his game and injuries as he crashed out of the SAP Open to Denis Istomin.
The former world number one, trying to find his form again after an injury-ravaged start to the season, smashed one racquet, broke another and argued with the chair umpire as he bowed out at the quarter-final stage 6-2 6-4.
Roddick, who is battling a right ankle sprain and a troublesome hamstring that forced his retirement from last month's Australian Open, said he would still play in next week's ATP Tour event in Memphis, despite his problems.
"It would be abnormal if you weren't frustrated," said Roddick, who also shouted back at his coaching box during Friday's defeat.
"The question is 'How do you figure your way through it?'"
Teenage American star Ryan Harrison cruised through his last-eight tie with Dimitar Kutrovsky, winning 6-1 6-4 to move to within two wins of his maiden ATP title.
But big-serving Canadian Milos Raonic stands in his way, the defending champion having knocked South Africa's Kevin Anderson out in straight sets 7-5 7-6 (7/3).
France's Julien Benneteau came from behind to defeat Steve Darcis 3-6 6-1 6-2 to set up his semi-final clash with Roddick's conqueror Istomin.