The 30-year-old Djokovic needed treatment on his right shoulder after the fifth game of the third set and a medical timeout at 4-3 to treat the same problem.

He had already summoned the doctor after just three games of the opening set.

Second seed Djokovic will face the Czech Republic's Tomas Berdych on Wednesday for a semi-final spot, boasting a 25-2 career record over the 2010 Wimbledon runner-up.