The Cricket World Cup looms large for both South Africa and Sri Lanka when they meet in the first one of the five-match ODI series starting at the Wanderers Stadium on Sunday.

While South Africa will be keen to get back to winning form after shock losses to the Lankans in two home Tests, both teams appear to be undecided on their best 15 players for the World Cup in England and Wales, starting in May.

South Africa have picked a 14-man squad packed with bowlers for the first three internationals, indicating the matches could help decide their best bowling combinations for the World Cup, while Sri Lanka have a squad of 17 players, two more than they can take to the global event.

Both teams have moderate recent records. South Africa have won 12 and lost 10 matches since the start of 2018, while Sri Lanka have six wins, 13 losses and a no-result in the same period.

South Africa's one-day squad includes only five of the players who appeared in the Tests and Sri Lanka have retained only seven of the victorious Test team - but Sri Lanka's Test wins are sure to add spice to the series despite the change in format and likely conditions.

South Africa will welcome a return to the faster pitches of Johannesburg and Centurion, venue of the second match, after losing the Test matches on the slower surfaces of Durban and Port Elizabeth, where the third and fourth matches will be played.

Fast bowlers Lungi Ngidi and uncapped Anrich Nortje, both recovered after long-term injuries, could provide a challenge to the Sri Lankan batsmen, while veteran Dale Steyn will be keen to show that he is still worth a World Cup place.

The South African selectors will be monitoring the fitness of JP Duminy, regarded as a key player if South Africa are to challenge at the World Cup.

He was due to return to domestic cricket with the Cape Cobras on Friday after missing most of the season because of a shoulder injury.

Sri Lanka's squad has been bolstered by the inclusion of experienced players Malinga, Upul Tharanga and Thisara Perera who did not play in the Tests.