Novak Djokovic was forced to retire from his Dubai Tennis Championships quarter-final against Feliciano Lopez.
The world number suffered 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.
"It started with an infection and then severe allergy," said Djokovic.
"I have had it ever since I arrived in Dubai. It's gotten worse in the last two days, unfortunately. It's the first time that I have had such a problem with the eye.