Usman Khawaja pulls during his maiden Test fifty, South Africa v Australia, 2nd Test, Johannesburg, 4th day, November 20, 2011© AFP
Imran Tahir celebrates Usman Khawaja's wicket, South Africa v Australia, 2nd Test, Johannesburg, 4th day, November 20, 2011© AFP
Ricky Ponting ended the fourth day with a half-century, South Africa v Australia, 2nd Test, Johannesburg, 4th day, November 20, 2011© AFP