Australia 8 for 275 (Watson 82, Finch 76, Smith 67, Peterson 4-32) beat South Africa 6 for 280 (De Kock 107, Behardien 63, Rossouw 51, Cummins 3-54) by 2 wickets (D/L method)
Scorecard and ball-by-ball details
Australia will enter the World Cup year ranked as the game's top ODI team and with the likes of Steve Smith, Aaron Finch and Shane Watson all running into ominous form, following a fourth victory in five matches over a sloppy South Africa at the SCG.
The hosts had more to play for in this fixture than the visitors, and it showed during their chase of 275, reduced from 281 by the second of two brief showers for the day. Finch, Watson and Smith all struck the ball cleanly, though the latter's sublime run of scores was maintained partly by some ordinary work in the field by a South African side missing AB de Villiers and Dale Steyn.
Morne Morkel's confidence ebbed away, as epitomised by a dreadful misfield to concede a boundary to Smith, who was also bowled off a Kyle Abbott no-ball and edged Morkel behind though the South Africans did not deign to appeal. Finch and Watson gave less chances, both working their way into decent touch after slow starts to the summer.
There was less promising news for Glenn Maxwell and the stand-in captain George Bailey, who each entered the match short of runs and confidence and will return to their states wondering who will be the man to make way for Michael Clarke, should he return in the new year. A late slide to the doughty left-arm spin of Robin Peterson briefly allowed South Africa to sense victory, before James Faulkner struck the winning boundary.
Quinton de Kock had played with poise and timing to guide the visitors' innings, receiving decent support from Rilee Rossouw, who had been included in de Villiers' place. Farhaan Behardien chimed in with a freewheeling 63 at the finish, an inside out drive over cover for six from Mitchell Starc the shot of the innings.
Having won the series in Melbourne, Australia's bowlers lacked a little in the way of penetration, though Pat Cummins again bowled usefully through the middle of the innings and deserved his three wickets.
Finch and David Warner began as though keen to end the match as quickly as possible, crashing boundaries to most corners of the SCG before a Warner miscue off Wayne Parnell was held expertly by Robin Peterson at mid on.
Watson has taken his time finding his rhythm after an off season extended by ankle and calf complaints, but timed the ball nicely in Sydney and was accompanied by Finch until almost halfway to the target. Australia were within 21 runs when Smith was dismissed, but the loss of 4 for 3 including Maxwell and Bailey caused a brief heart flutter for the hosts.
Still, the team's finisher Faulkner remained at the crease, and he swung the first ball of the final over by Peterson to seal the match, the series and the No. 1 ranking.
Hashim Amla had called correctly at the toss because South Africa chose not to risk de Villiers after he suffered a rib complaint in the fourth match at the MCG, which Australia won to seal the series. Steyn was also rested having played the first four matches, meaning a return to the team for Morkel.
Australia made one change to the team that won from a long way back at the MCG, recalling Josh Hazlewood for the injured Nathan Coulter-Nile. A perfect day and an evenly grassed pitch greeted the teams, though the crowd was again a slim one.
De Kock knew it would be his day from the first ball he received, a yorker from Starc that he jammed down upon, squeezing it narrowly past the stumps and down to the fine leg boundary. He was more comfortable against Josh Hazlewood and James Faulkner, while also carting 11 from Shane Watson's single over.
Amla was content to bat in de Kock's slipstream early on, but his attempt to push along resulted in his wicket when a fierce drive at Glenn Maxwell resulted in an outside edge that was very well held by Matthew Wade up to the stumps.
Rossouw played diligently in support of de Kock, and looked good for more than his 51 when the calling of the batting powerplay caused him to miscue a pull shot to mid on. The shower came and went, and on resumption Faf du Plessis picked out George Bailey at cover.
These reverses could not detract from de Kock's innings, and after his dismissal touching an attempted upper cut at Cummins through to Wade, Behardien provided a reminder of why he is in South Africa's World Cup plans. Had Steyn been playing and South Africa sufficiently sharp, the chase may have been more challenging than it proved.