Ammon News - The 34-year-old announced his withdrawal on Twitter; his decision coincided with Roger Federer's decision to pull out of the ATP Cup entirely; Nadal is hopeful of returning to action on Thursday when Spain take on Greece.

Rafael Nadal has withdrawn from Spain's opening match at the ATP Cup in Melbourne due to a bad back.

The world No 2 announced on Twitter that the decision had been taken for him not to feature in the opening Group B match against hosts Australia.

"Hi all, we have decided with #TeamSpain and my team, to not play today the first match of the @ATPCup here in #Melbourne since I have a stiff low back. Hopefully I'll be better for Thursday. We have a strong team, all the to @pablocarreno91 @BautistaAgut & @M_Granollers #vamos," he wrote.

Greece are the opponents for Spain on Thursday as players continue to prepare for the Australian Open, which gets under way next Monday.

Roger Federer is also injured and withdrew from the ATP Cup - but the remainder of the world's top 10 players are competing, including No 1 Novak Djokovic.

*SKY