Johannesburg: Uncapped off-spinner James Tredwell was called into the England squad as cover on Thursday after Graeme Swann and Stuart Broad were ruled out of the first two One-Day Internationals through injury.
Spinner Swann has a side strain and pace bowler Broad a shoulder injury.
Tredwell, 27, will vie with leg-spinner Adil Rashid, who conceded 25 runs in his only over in the second Twenty20 international, for the opening One-dayer on Friday.
"James Tredwell is definitely an option. Being a right-arm off-spinner and with quite a few left-handers in the South African line up, his ability to spin the ball away is important," England captain Andrew Strauss said.
"He has deserved his chance, he has performed very well for Kent over a long period of time and is a very canny One-day operator.
"But Adil Rashid is improving all the time and the more exposure he gets the better. He needs to play too, but it's important that we get the right player for the game. Clearly, it's important that we have both options." Strauss said.
South African coach Mickey Arthur said he expected 21-year-old Rashid to play.
England won the first, rain-affected Twenty20 international by a single run last week. South Africa reversed some of that momentum by scoring 241 on their way to an emphatic 84-run triumph at Centurion in the second match.