South Africa skipper Faf du Plessis on Wednesday said the absence of veteran pacer Dale Steyn from their World Cup opener against hosts England will be a big loss and will force a change in their game plan.
"He is a big loss to our team," du Plessis told reporters here on Wednesday.
"He was probably about 60 percent when the squad was picked so we anticipated for this to happen, but a fit Dale Steyn makes our bowling attack a very, very strong one. So tomorrow will be a little bit of chopping and changing."
Du Plessis will lead his side out at The Oval against the world's top-ranked team, which is also chasing its maiden World Cup trophy.
England have won 15 of their last 19 ODI series and are the team to beat on home soil.
'Chokers' is a tag South Africa have been used to at World Cups as they are also chasing their first trophy
"Whether you are favourites or not, you still have to play good cricket. They deservedly have the tag because they are the home nation and have consistently played good cricket," said du Plesssis.
"But you will face such different opposition through this tournament so it is about making sure you stay focussed for the whole tournament. England are the favourites so if it means on the day there is less pressure on us then we can play freely.
"We are going in as underdogs and if that releases some players in the team then that is great."
For South Africa to stop England in their tracks, taking wickets will be essential.
England captain Eoin Morgan claimed their current top seven is the best they have ever had and much of the pre-tournament talk has surrounded the prospect of them becoming the first side to score 500 runs in ODI cricket.
The loss of seamer Steyn is a further boost for England, with the 35-year-old ruled out with a shoulder injury.
However, South Africa still boast a formidable pace attack led by Kagiso Rabada.
"KG does not need any guidance from me. I can speak to him from a tactical point of view but I won't tell him how to bowl, he knows more than I do.
"It is about setting him free. World Cups are for people to perform and KG will want to make this his stage. Dale is a big loss to our team but we expected it.
"But a fit Dale Steyn makes our attack a strong one so we need to make a few changes to our team for England. Our bowling is one of our X-factors," the skipper added.