Roddick into Open semis after Davydenko retires

American second seed Andy Roddick qualified for the Australian Open semi-finals after his opponent Nikolay Davydenko retired during the third set on Wednesday.

Roddick was leading the ailing Russian 26th seed 6-3, 7-5, 4-1 at the time Davydenko called a halt with apparent breathing problems in the stifling conditions on Rod Laver Arena.

The 2003 US Open champion will now face the winner of late Wednesday's remaining quarter-final between Australian third seed Lleyton Hewitt and Argentine number nine seed David Nalbandian in Friday's semi-final.

Davydenko battled with the condition during the match and frequently called on the trainer and tournament doctor for treatment during changeovers.

He used an inhaler several times and donned an ice vest to help cool his body during changeovers in the second and third set.

But once Roddick broke his service for a second time in the third set and with the outcome a virtual certainty, Davydenko walked towards the chair umpire Lars Graff and called a halt.

Up until that stage Roddick had too much firepower for Davydenko serving at around 66 percent and coming up with 17 aces in the 1hr 35min contest.

Roddick broke Davydenko's service five times during the match, and clocked a fastest serve in the balmy conditions at 229 kmh (142 mph).

It is 22-year-old Roddick's second appearance in the last four of the Australian Open after he was beaten by German Rainer Schuettler in the 2003 semi-final.

He ran out of gas after his monumental five-hour quarter-final victory over Moroccan Younes El Ayanoui which was decided 21-19 in the fifth set.

But Roddick won't have the problems of fatigue in Friday's semi-final having spent a total of 7hr 42min on court in this year's grand slam.

Davydenko went into Wednesday's match with the breathing problem after coming through his round of 16 match with Spanish 12th seed Guillermo Canas in straight sets.

Up to Wednesday's quarter-final 23-year-old Davydenko had not dropped a set in his four wins here, highlighted by his straight sets elimination of British seventh seed Tim Henman in the third round.