Second seed Andy Roddick reached the semi-finals of the Australian Open today after Russian Nikolay Davydenko retired in the third set of their match because of breathing problems.
The American was leading 6-3 7-5 4-1 when Davydenko, who began showing signs of distress early in the second set, decided to quit.
Roddick had been forced to save a set point in the second set but was well on top when the Russian called it a day.
The American will now play the winner of tonight's match between third-seeded Australian Lleyton Hewitt and ninth seed David Nalbandian of Argentina.
