Marat Safin, the holder, and Rafael Nadal are both doubts for the Australian Open which starts at Melbourne Park on 16 January because of injury.
Safin is increasingly unlikely to defend his title because of a knee injury which has kept him off court since August. The Russian yesterday announced his withdrawal from the Hopman Cup, one of the lead-up events to the Open.
Nadal has withdrawn from next week's season-opening Chennai Open because of a foot injury. The world's No 2 has failed to recover from the injury he sustained in the Madrid Masters final in October.
Goran Ivanisevic could become captain of Croatia's Davis Cup team this week, replacing Nikola Pilic, who led the country to the title this year. Ivanisevic said yesterday "as things stand now, it is likely that I will take over" the post, while Pilic would remain as an adviser. A final decision is expected today when Ivanisevic, the 2001 Wimbledon winner, meets with the head of the Croatian Tennis Federation.