South Africa will continue to experiment in their quest to get the right balance for this year's Cricket World Cup when they face Pakistan in the three remaining ODIs and in the coming five against Sri Lanka.

Captain Faf du Plessis said yesterday they have not yet finalised places for the World Cup opener against hosts England at the Oval on May 30.

He added that they are faced with tough decisions in picking a squad that will go all out to win the global tournament later this year.

As the Proteas prepare for the third ODI against Pakistan at SuperSport Park today, Du Plessis said they have many tricky things to consider as they attempt to balance the team.

"If you look at the balance of the side, you'll have an extra fast bowler and extra spinner," he said.

"We have the extra spinner but we are still looking at the fast bowler.

"The all-rounder will be the extra guy and we have to make a call on whether he is an extra batter or keeper batter.

"That gets a bit tricky and interesting," said Du Plessis.

"We have said it before that closer to the Pakistan series we wanted to be near a team that will play at the World Cup but injuries have not made that possible and we had a few players coming in."

The injury to fast bowler Lungi Ngidi has forced the think tank to look elsewhere.

The emergence of batsman Rassie van der Dussen has increased competition in the batting department while Andile Phehlukwayo looks interested in taking the all-rounder spot.

"The fact that Lungi got injured opened a slight gap to look at who is the next guy," Du Plessis said.

"Because he is not available for this series, we expect him back for the next series against Sri Lanka, so we had to look at who else is out there.

"Before the series, Reeza Hendricks and Aiden Markram were in a shootout for a place in the top order and now we have added Rassie.

"Rassie has taken the opportunity with both hands by scoring runs." he said.