November 9, 2014, Sydney
Start time 19:35 local, 08:35 GMT
This Twenty20 series has fluctuated in a near miniature version of the Test series between Australia and South Africa earlier this year. The visitors were commanding in game one, the hosts domineering in game two. What remains to be seen is whether the script will be maintained, with the tourists finding their feet in time to deliver the knock out blow in the decider. South Africa's captain JP Duminy has termed the swings and roundabouts an education - he will hope his men have learned enough by now.
Australia's victory at the MCG was based on the classical combination of energetic pace bowling and nifty wrist spin twirled down by Cameron Boyce. Their combination limited South Africa to a tally they had no real hope of defending, and so the securing of a better start will be critical for Duminy's team. The hosts also benefited from the promotion of Ben Dunk to open in place of Cameron White, allowing the batsman-keeper to play in the role with which he is most familiar.
Sydney's Olympic Stadium has notably short straight boundaries, favouring batsmen who can drive powerfully and straight. The drop-in pitch can often be a somewhat slow and amenable to variations from seamers, so there may be the odd slower ball bouncer delivered on Sunday.
Form guide (most recent matches first)
South Africa LWLWW
In the spotlight
Parachuted back into the team for the MCG, Glenn Maxwell finished up with very little to do, and made a duck during Australia's successful chase. He will expect better on Sunday with the benefit of another two nights' sleep after his return from the UAE, and many will be hoping to see Maxwell's talent harnessed after a week in which his defence of some absent-minded stroke selection against Pakistan has again highlighted his ambitious but occasionally adolescent batting ways.
Flying high in Adelaide, JP Duminy and his team were brought to earth with a considerable thud in Melbourne. As a new captain, Duminy's ability to guide the tourists through the highs and lows of the past few days to a settled display in Sydney will be watched closely by many, not least South Africa's selectors. It would help to make some runs of course - scores of 6* and 49 suggest a substantial contribution is in the offing on the most crucial occasion of the series.
An unchanged XI seems like for Australia given their wide margin of victory in Melbourne.
Australia (possible): 1 Aaron Finch (capt), 2 Ben Dunk (wk), 3 Shane Watson, 4 Glenn Maxwell, 5 Cameron White, 6 James Faulkner, 7 Sean Abbott, 8 Pat Cummins, 9 Kane Richardson, 10 Cameron Boyce, 11 Doug Bollinger
Marchant de Lange may come into the side after sitting out the first two matches.
South Africa (possible): 1 Quinton de Kock (wk), 2 Reeza Hendricks, 3 Rilee Rossouw, 4 JP Duminy (capt), 5 David Miller, 6 Farhaan Behardien, 7 Ryan McLaren, 8 Imran Tahir, 9 Wayne Parnell, 10 Kyle Abbott, 11 Marchant de Lange
Stats and trivia
This will be South Africa's first match at Sydney Olympic Stadium
In three T20Is at the stadium, the smallest crowd has been 40,242 for Sri Lanka's win over Australia in January 2013
"In some ways I'm happy that we experienced this. It was all bells and whistles after the first game, everyone was on a high so it's good to experience this, especially as a young side. We need to come back stronger on Sunday."
South Africa's captain JP Duminy tries to take a positive from his side's heavy defeat in game two
Daniel Brettig is an assistant editor at ESPNcricinfo. @danbrettig