<p>World number two Rafael Nadal pulled out of Spain's opening ATP Cup tie against Australia Tuesday, complaining of a stiff lower back.</p>.<p>The 20-time Grand Slam champion was due to take the court against Australia's top-ranked player Alex De Minaur but opted to rest instead as he prepares for the Australian Open next week.</p>.<p>"Hi all, we have decided with Team Spain and my team, to not play today the first match of the ATP Cup here in Melbourne since I have a stiff low back," he tweeted.</p>.<p>Nadal added that he hoped to have recovered by Thursday when Spain meet Greece.</p>.<p>Spanish number two Roberto Bautista Agut will now face de Minaur, while John Millman takes on Pablo Carreno Busta in the opening rubber.</p>.<p>Nadal, who is aiming for a record-breaking 21st Slam title in Melbourne, moving him past the injured Roger Federer, played an exhibition in Adelaide on Friday, beating Dominic Thiem 7-5, 6-4.</p>
<p>World number two Rafael Nadal pulled out of Spain's opening ATP Cup tie against Australia Tuesday, complaining of a stiff lower back.</p>.<p>The 20-time Grand Slam champion was due to take the court against Australia's top-ranked player Alex De Minaur but opted to rest instead as he prepares for the Australian Open next week.</p>.<p>"Hi all, we have decided with Team Spain and my team, to not play today the first match of the ATP Cup here in Melbourne since I have a stiff low back," he tweeted.</p>.<p>Nadal added that he hoped to have recovered by Thursday when Spain meet Greece.</p>.<p>Spanish number two Roberto Bautista Agut will now face de Minaur, while John Millman takes on Pablo Carreno Busta in the opening rubber.</p>.<p>Nadal, who is aiming for a record-breaking 21st Slam title in Melbourne, moving him past the injured Roger Federer, played an exhibition in Adelaide on Friday, beating Dominic Thiem 7-5, 6-4.</p>