Novak Djokoivc was forced to retire from his Dubai Tennis Championships quarter-final against Feliciano Lopez.
The world number one appeared to be suffering from an eye problem and quit after losing the first set 6-3.
A day on from his 700th career win, Djokovic's run of making 17 successive Tour finals came to an end after making 18 unforced errors in only nine games against the sixth seed.
Spaniard Lopez will now face Cypriot Marcos Baghdatis in the semi-finals.
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