What a difference two weeks can make. Before the first Test, in mid-February, the question was not whether Sri Lanka might surprise their hosts, but by how much South Africa were going to beat a touring team who arrived battling multiple crises. Sri Lanka have, of course, made history since then, setting up their Test series with that miraculous 10th wicket stand in Durban and then taking it home in Port Elizabeth to become the first Asian side ever to win a Test series here. A first limited-overs series win for them might have been unthinkable when they arrived. Now, it's a distinct possibility.
It was all going so well for South Africa after their triumph across formats against Pakistan. But their seven-series long winning streak at home was brought to a rude end, and the feel-good knock-on effect of the summer has subsequently been knocked back by recent events - including Duanne Olivier's departure for Yorkshire.
They do still have plenty of depth in their fast bowling ranks, and with Lungi Ngidi back to full fitness and Anrich Nortje likewise fit and able, it's unlikely Olivier would even have had a role to play in the ODI series.
South Africa's coach and captain have made sure to keep their Test and one-day plans quite separate, and whatever questions might have been raised by their defeats to Sri Lanka, Faf du Plessis and Ottis Gibson know that they will not be answered until the team's next Test engagements at the end of the year. There are much more urgent, immediate matters to attend to. South Africa have just five ODIs scheduled before their World Cup opener against England - five more games to find out who their best XI are and crystallise the final version of Vision 2019.
Sri Lanka, meanwhile, will play two more against Scotland just before the World Cup, so they have a little more breathing room as they assemble their own World Cup squad. They also have plenty of ground to make up, having not won an ODI series since the tri-nation tournament against Bangladesh and Zimbabwe a year ago. They have not won a bilateral series for almost two-and-a-half years. In unlikely circumstances, it's not far fetched to suggest they might have a decent shot of turning that record around, starting from Sunday.
South Africa WLWWL (completed matches, most recent first) Sri Lanka LLLWL
In the spotlight
While South Africa continue to search for the best top six and all-round options, one thing they're definitely not short of is quality quicks - even after Olivier's exit. The latest in the production line is Anrich Nortje, who was virtually unknown outside of South African domestic cricket until the Mzansi Super League, but has since picked up an IPL contract and, in all likelihood, an international debut. Nortje has the pace to trouble any top order, and he will want to make a strong start with a World Cup spot potentially up for grabs.
While Nortje is an unknown, Sri Lanka will be led by one of the most famous cricketers on the planet. Lasith Malinga celebrated his arrival for his third trip to South Africa by picking up 5 for 35 in the warm-game against the Cricket South Africa Invitation XI. Always watchable, and one of the canniest bowlers to have played one-day cricket, Malinga will be key to Sri Lanka's success.
Ngidi and Nortje are the only new or returning faces in South Africa's squad, and both are likely to be part of the starting line-up on Sunday. Their presence suggests it is likely South Africa could rest either Kagiso Rabada or Dale Steyn, who played the Test series.
South Africa (possible): 1 Quinton de Kock (wk), 2 Reeza Hendricks, 3 Rassie van der Dussen, 4 Faf du Plessis (capt), 5 David Miller, 6 Wiaan Mulder, 7 Andile Phehlukwayo, 8 Kagiso Rabada/Dale Steyn, 9 Anrich Nortje, 10 Lungi Ngidi, 11 Imran Tahir
Akila Dananjaya's action has been cleared following tests on his action in Chennai and he should slot straight back into the lower middle order.
Conditions in the last ODI at Johannesburg suited Pakistan a little more than it did the hosts, the visitors cruising to an eight-wicket win on a dry track. Since then, the two domestic one-day games scheduled here were both rained off, so quite how the track will play on Sunday is difficult to call. Usually, the ball flies around on the highveld and the game could be high-scoring. The weather should also be set fair.
Stats and trivia
Sri Lanka have won two of the five ODIs they've played against South Africa at the Wanderers, coming out on top in 2001 and 2012
Kumar Sangakkara is the only Sri Lankan batsman to have scored an ODI hundred at the Wanderers
Faf du Plessis is the leading run-scorer against Sri Lanka in ODIs in the current South African ODI squad, with 798 runs at 44.33