Dambulla - Sri Lanka captain Angelo Mathews won the toss and elected to bat against South Africa in the first one-day international in Dambulla on Sunday.
LIVE: Sri Lanka v Proteas, 1st ODI
The hosts, upbeat after a 2-0 whitewash of the Proteas in the Test series, included two fast bowlers and two spinners in their starting eleven.
"We have the (2019) World Cup at the back of the mind for sure, so we'll try a few combinations," Mathews, who last played an ODI in January, said at the toss.
"We're good to go and I'm looking forward to it."
Visiting skipper Faf du Plessis said South Africa's disappointing show in the Tests will not affect their chances in the five ODIs.
"The Tests shouldn't affect our game. A young squad, (a) lot of energy, and that excites me. Even if they make mistakes, it's about getting better and learning from them," said du Plessis.
Sri Lanka: Angelo Mathews (captain), Upul Tharanga, Kusal Perera, Kusal Mendis, Niroshan Dickwella (wicketkeeper), Thisara Perera, Shehan Jayasuriya, Akila Dananjaya, Suranga Lakmal, Lakshan Sandakan, and Lahiru Kumara.
South Africa: Faf du Plessis (captain), Hashim Amla, Quinton de Kock (wicketkeeper), Aiden Markram, Jean-Paul Duminy, David Miller, Willem Mulder, Andile Phehlukwayo, Kagiso Rabada, Tabraiz Shamsi, and Lungi Ngidi.
Umpires: Nigel Llong (ENG), Ruchira Palliyaguruge (SRI)
TV umpire: Paul Reiffel (AUS)
Match referee: Javagal Srinath (IND)