Russia's Nikolay Davydenko has been fined $10,000 for making negative comments about Sydney's $1.2 million tennis tournament.

The world number three told reporters on Wednesday that some of the sport's top players had pulled out of the last major warm-up for next week's Australian Open because they did not care about the event.

ATP chairman Etienne De Villiers, head of the body which governs men's tennis, said he was concerned about the high withdrawal rate in Sydney but that Davydenko's comments were harmful.

"I'm satisfied that the $10,000 fine for Davydenko is the appropriate sanction for the comments that were made that not only damaged the very fine tournament in Sydney but also sullies the reputation of our great sport," De Villiers said in a statement on Thursday.

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 Sydney event in 24 hours, joining Spanish world number two Rafael Nadal, fellow Russians Svetlana Kuznetsova and Nadia Petrova, and Thailand's Paradorn Srichapan.

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 in practice.

WITHDRAWAL CONCERNS

Each of the other retirees said they expected to recover in time for the Australian Open, but Davydenko drew the ire of the sport's world governing body for suggesting players were using their injuries as an excuse to save themselves for Melbourne.

De Villiers, who has vowed to crackdown on players retiring from events, said he would investigate the reasons behind the mass exodus in Sydney.

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

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

"I will address this again at the mandatory players meeting in Melbourne at the weekend and at the ATP Player Council."

Davydenko's comments also drew a stinging rebuke from American 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 have those people that are paying the money, you'd want to show them the respect because they're the ones that are paying the tickets so we can get sponsorships, so we can get it on TV so we can be millionaires."