Davydenko pulled out of the event on Wednesday

He claimed on Wednesday that players had pulled out of the last major warm-up for the Australian Open because they did not care about the event.

ATP chairman Etienne De Villiers said he was concerned about the withdrawal rate but the comments were harmful.

"They not only damaged the very fine tournament in Sydney but also sullied the reputation of our sport," he said.

Davydenko pulled out of the Sydney tournament on Wednesday after losing the first set of his second-round match with Frenchman Paul Henri-Mathieu, citing a foot injury that doctors fear may be a stress fracture.

Should the injury be confirmed as a fracture, Davydenko faces six weeks out of the game.

He was the fifth player to retire from the event in 24 hours, joining Spanish world number two Rafael Nadal, fellow Russians Svetlana Kuznetsova and Nadia Petrova, and Thailand's Paradorn Srichapan.

On the face of it, it seems some players are still looking at the event as an option rather than a commitment Etienne De Villiers

Australia's Lleyton Hewitt withdrew on the eve of the tournament, citing a calf problem, Russian Dmitry Tursunov pulled out before his match after injuring his wrist.

Davydenko suggested players were using their injuries as an excuse to save themselves for the Australian Open.

De Villiers, who has vowed to crack down on players retiring from events, said he would investigate the reasons behind the withdrawals in Sydney.

"I remain concerned about the withdrawals," he said.

"I need to better understand the reasons but on the face of it, it seems some players are still looking at the event as an option rather than a commitment."

Davydenko's comments were criticised by James Blake, who won the Sydney title in 2006 and is vice-president of the ATP Player's Council.

"It is a bit disconcerting to hear someone talk about a tournament and not show the respect it deserves, especially when they're playing here," Blake said.

"You would think you would want to show respect to those people paying the money for the tickets so we can get sponsorships, so we can get it on TV and so we can be millionaires."

Blake reached the semi-finals with a 6-1 6-4 win over Russian Evgeny Korolev and will now play Jurgen Melzer after the Austrian overcame Tomas Berdych 6-2 6-4.

Spaniard Carlos Moya also reached the last four after ousting fourth seed Marcos Baghdatis 6-1 3-6 7-6 (7-3).

Baghdatis twisted his ankle in the deciding third set but after receiving treatment, was allowed to continue.

"I thought I twisted a tendon behind the left ankle," said Baghdatis, who reached the final at last year's Australian Open.

"But then it went up to the calf and slowly, slowly it was getting better and better."

The final quarter-final saw Frenchman Richard Gasquet defeat Paul-Henri Mathieu 6-4 6-7 (1-7) 6-0.