Olympics - Wawrinka pulls out and Groth gets call

World number four Stan Wawrinka has pulled out of the tennis competition at this month's Rio Olympics because of injury. "I am very sad because after Beijing and London I would have liked to experience my third Olympic Games in Brazil, unfortunately that will now not be possible," he said in a Swiss Tennis Federation statement on Tuesday. Australia's Sam Groth is heading to Brazil after getting a late call as a replacement.