Melbourne, Dec 27: Mitchell Johnson hit a confident half century to steady Australia to 440-8 and a 284-run lead over Sri Lanka at stumps on Thursday following a mid-order collapse on the second day of the second test.
Johnson followed his four wickets on the first day with an enterprising knock of 73 with six boundaries after Sri Lanka claimed three wickets for just four runs before tea.
Michael Clarke earlier brought up his 22nd test century and first at the Melbourne Cricket Ground after becoming Australia's highest-ever run scorer in a calendar year.
Clarke and Shane Watson shared a 194-run partnership until the Australia captain edged a Shaminda Eranga (2-106) delivery with the new ball to Mahela Jayawardene at third slip for 106.
Watson fell for 83 in the next over when he hooked a lofted shot off Dhammika Prasad (3-102) to the waiting hands of Thilan Samaraweera at deep square leg.
Matthew Wade added just one run before becoming Prasad's third victim of the test, caught by Eranga (2-106).
David Hussey made 34 in a 61-run, seventh-wicket stand with Johnson before falling to a superb one-handed, diving catch by Rangana Herath at the boundary off a Tillakaratne Dilshan (1-38) ball.
Johnson and Peter Siddle (13) put on a 58-run partnership for the eighth wicket until Siddle fell just before stumps.