<div><p>MELBOURNE (Reuters) - Defending champion Serena Williams produced a remarkable fightback from a set and 4-0 down against Victoria Azarenka to reach the semi-finals of the Australian Open on Wednesday.</p><p>The world number one, initially bullied by the seventh seed from Belarus in their quarter-final, came through 4-6 7-6 6-2 and will meet China's Li Na for a place in the final.</p><p>Li had earlier knocked out Williams's older sister Venus on Rod Laver Arena.</p><p>Serena appeared sluggish until Azarenka held serve to take her 4-0 lead in the second.</p><p>That seemed to finally wake up the top seed who won five straight games to take the set before she blowing the 20-year old off court in the decider.</p><p>(Reporting by Greg Stutchbury; Editing by Alastair Himmer)</p><img src="http://admatch-syndication.mochila.com/images/ad.gif?aid=67872147&bid=informcom" /></div><div id="copyright"><div>

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