Roger Federer has been knocked out by German world No.55 Daniel Brands in his opening match of the Swiss Open.
Federer suffered a shock 6-3 6-4 defeat to Brands, who completed the beating of Federer in just 66 minutes.
Federer is on an extremely poor run of form, having lost to Argentine qualifier Federico Delbonis in Hamburg just last week.
31-year-old Federer still holds the record of most single Grand Slam major titles with 17, however recently slipped out of a top four world ranking for the first time since 2003.
Federer has revealed he has been experiencing back pain that has been affecting his performances.
"I've had serious problems with the back, I had to get some anti-inflammatories last week in Hamburg due to the back pain," said Federer.
"It was so tough to play and move out there today. I'll just have to take treatment and see how it all goes."
2013 is turning out to be tough year for the Swiss player - the 31-year-old has only won the Halle title this year and his worrying dip in form comes a month before the US open.
Federer won Wimbledon 2012 beating Andy Murray in a tense finale, however his form from then onwards has been somewhat indigent.
Daniel Brands will now play against Romanian Victor Hanescu in the quarter-finals of the Swiss Open.
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