Serena Williams failed to progress to the semi-finals of the Cincinnati Open after losing to Angelique Kerber in the last eight on Friday.
Williams lost in straight sets 6-4 6-4, losing her 19-match winning streak at the Western & Southern Open in the process.
The match also saw the 30-year-old lose her first set since winning the Wimbledon in July.
However, her sister Venus progressed to the last-four of the competition after defeating Samantha Stosur in straight sets.
Williams won gold medal in women's singles at the London Olympics earlier this month.
