Nick Kyrgios was forced to retire hurt at the end of the third set against Illya Marchenko.
Kyrgios had won the first set 6-4 with some brilliant tennis, but picked up a hip injury in the second set.
He took time off court to receive treatment, but returned to inform the umpire that he felt like he had been “hit by a bus”.
He continued to play, though, despite his movement towards the forehand being severely limited, and his opponent made the most of it.
Marchenko was two sets to one up, 4-6 6-4 6-1, when Kyrgios finally admitted he was unable to continue.
The 14th seed complained of the injury during his first two matches and said he felt like he’d been ‘hit by a bus’ at one point during Saturday’s defeat.
The loss was Kyrgios’s first in 21 matches against unseeded opponents at grand slam events and will come as a bitter disappointment for the 21-year-old who had high hopes at the Open.