Herschelle Gibbs scored an unbeaten century as South Africa crushed Sri Lanka by eight wickets to take an unassailable 3-1 lead in this five-match series at the De Beers Diamond Oval on Wednesday.
Sri Lanka had high hopes of leveling the series here after a resounding win in third game at Benoni but a combination of ill-fortune, electric fielding and sloppy batting now leaves them fighting for only pride in the final game on Friday.
Sri Lanka threatened a competitive score after being asked to bat first, racing to 57 without loss after the first ten overs, but a freak run out sparked a dramatic top order collapse and they were bowled out for 184.
Such a meager target was never likely to be sufficient on a flat batting surface, but new ball bowlers Chaminda Vaas and Pulasthi Gunaratne sent jitters through the South Africa top order with the early wickets of Andrew Hall (2) and Neil McKenzie (7),
However, the experienced Herschelle Gibbs and Jacques Kallis quickly reasserted their authority over the visitors in a record unbroken 173 run partnership for the third wicket.
Gibbs, who came into the game with three successive failures in the series, finally hit form after an awkward start, smashing a succession of boundaries, including a remarkable punch over mid-wicket to bring up his 11th one-day century.
The right-handed opener finished with 108 from just 92 balls having hit 14 fours and three sixes.
Kallis has had no such problems with his form coming into the game and he carried on where he left off at Benoni, cruising to his third half-century of the series, finishing unbeaten 64 from 83 balls having hit five fours and a six.
Under pressure to take quick wickets, the discipline shown by Sri Lanka's bowlers last Sunday evaporated and South Africa reached their target with an embarrassing 19.1 overs to spare.
But it was the batsmen who shouldered most responsibility for the defeat, like they did at Wanderers and Centurion where they were bowled out for an unacceptable 140 and 128.
They had started the day well enough with Marvan Atapattu playing gloriously against the new ball, driving through the covers on the up and cutting imperiously, as he raced to 39 from 46 balls.
But his purple form was wasted by a lackadaisical piece of running, as the right-hander was adjudged to have not ground his bat or foot the crease by television umpire Brian Jerling after a cheeky backwards flick from wicket-keeper Mark Boucher.
The Sri Lankans, who were seething immediately after the decision, will claim with some justification that there was too much doubt for Jerling to press the red light, but Atapattu was guilty of ignoring the basics as he failed to run in his bat properly after ambling back from a comfortable two.
The incident changed the course of the game, visibly rattling the impulsive Sri Lankans, who hit the self-destruct button, losing four wickets for just seven runs.
Kumar Sangakkara (1) pulled a Kallis long hop straight into the hands of square leg and Aravinda de Silva (0) followed his fine 71 in the last match with a duck as he top edged an attempted hook.
An astonishing one-handed airbourne catch by McKenzie - playing his first game of the series - then accounted for Jayasuriya (27 from 33 balls) and Mahela Jaywardene (9) was trapped lbw by Alan Donald to leave Sri Lanka on 97 for five.
Russel Arnold produced provided some timely resistance with the Sri Lankan selectors set to finalise their squad for Australia on Saturday, scoring 50 from 88 balls, adding 34 for the seventh wicket with Hashan Tillakaratne.
But the fight-back proved shortlived as Tillakaratne swung across the line against Pollock and was bowled. The rest of the tail were then blown away, although Gunaratne did add 29 for the last wicket with Arnold.
Donald was the most successful bowler, taking three wickets for 18 runs from his allotted ten overs. Pollock also claimed a three-for.