O'Keefe replaces Siddle for third Test
Left-armer O'Keefe joins fellow spinner Nathan Lyon in the XI for Sunday's clash at the SCG in Sydney after Siddle failed to overcome an ankle problem sustained during the 177-run win in the Boxing Day Test.
O'Keefe, 31, played his one and only Test against Pakistan in October 2014, taking four wickets.
Australia - leading 2-0 and looking to claim a series sweep - are now set to field two specialist spin bowlers for the first time since 2006.
"He [Siddle] felt it wasn't best for him to come into this Test match the way he is at the moment," captain Steve Smith said on Saturday.
"He's a great team man and felt he would be letting the team down [if he played].
"He'll have a rest for a couple of weeks and hopefully get himself right for [the upcoming tour of] New Zealand.
"We were probably going to go the two spinners option anyway."
Australia: Joe Burns, Josh Hazlewood, Usman Khawaja, Nathan Lyon, Mitchell Marsh, Stephen O'Keefe, Peter Nevill, James Pattinson, Steve Smith, David Warner, Adam Voges.