This is a bit of the battle of the unknowns here.
There have only been a handful of matches at Paarl. There have only been two matches between South Africa and Sri Lanka in the last 5 years. Both teams are somewhat unpredictable, and Sri Lanka are likely to have a vastly different line up to the test matches.
So it is hard to make too many predictions really.
However there are a couple of things to look for.
1. Dilshan hit 58 and 106 in his last two innings against South Africa. He is under some scrutiny as captain and needs a score. Will this be his time?
2. De Villiers is likely to bat at 4, keep wickets and captain his team. Dhoni and Sangakkara both proved that it is possible to succeed while keeping, captaining and batting in the top 5, but Gilchrist, Germon, Taibu and Flower all struggled with the excessive workload. De Villiers is certainly a talented batsman, but so were Gilchrist and Flower. It will be interesting to see if he can hold it all together.
3. Ajantha Mendis is likely to make a return. He's only bowled 7 overs against South Africa in any form of cricket, but he took 3 for 30 in those 7 overs, picking up Smith, Kallis and Duminy. If he can repeat this then Sri Lanka are in with a big show.
4. Lasith Malinga is playing his 100th ODI match. He has played 4 ODI matches against South Africa and taken 10 wickets, roughly one wicket every 3 overs. He is always an interesting bowler to watch, and it will be good to see how he goes in this match.
5. JP Duminy looking to get on the board. Duminy's last 4 ODI innings against Sri Lanka have been 3(3), 0(2), 0(1) & 0(1). He has faced 7 deliveries scored 3 runs and been out 4 times. However his last outing at Paarl was him guiding the Cape Cobras to a win with 52* at the end of a match, so he may be in a good space to turn that round.
Some betting tips.
In the three matches that have been played at Paarl between big teams, there have been 2 century opening partnerships and one 50 opening partnership. The 2nd wicket has been even more productive. If you are looking to be over on any batsman, make sure they are in the top three. Likewise don't think the game is over just because one team has a good start. Most teams get off to a good start at this ground.