England bowler Steven Finn looks set to miss the fourth Test against South Africa because of a side strain.
Finn, 26, felt some tightness in his left side during England's series-clinching victory at the Wanderers.
The Middlesex paceman was sent for scans on Sunday morning, with the results due on Monday.
Chris Woakes, Chris Jordan or Mark Footitt could replace him for the final Test, which starts at Centurion on Friday, as England target a 3-0 win.
"I doubt very much whether he'll be available for the next Test," said England head coach Trevor Bayliss.
"We'll have to wait and see how bad it is and make a decision on the one-day and Twenty20 series.
"But at this stage it looks like we have to make a replacement heading into the last Test. That's unfortunate because I thought he was probably our most dangerous bowler in the first two Tests."
Finn was not in the initial squad for the South African tour after missing last year's series against Pakistan with a bone stress injury in his left foot.
But he was called up in mid-December after proving his fitness and took 11 wickets at an average of 26.09 in the first three Tests.
Bayliss backs Hales and Compton
The fourth Test will present another opportunity for Alex Hales and Nick Compton, who were brought into the England top three for the South Africa series, to cement their places in the side.
Compton, batting at three after a two-and-a-half-year absence, made 85, 49 and 45 in his three first Test innings of the tour, but has since passed 26.
The 32-year-old, who has the second-lowest strike-rate of any batsman to have played 20 innings in England's top three since 1980, fell for a duck trying to complete the run chase in Johannesburg with a loft down the ground.
"I was quite happy with what he tried to do," said Bayliss. "It sent a message that he was playing for team.
"The boys were having a joke about the chances of him hitting a six to win the game, then we thought he might have done it. It was a good catch to get him out.
"He's done pretty well. He's a solid cricketer and with him and Alastair Cook in the order, the rest of the attacking players can bat around them."
Hales, who made his debut in the first Test and became Cook's eighth opening partner in three years, has made 120 runs in six innings, including a maiden half-century in the second Test.
"He's done reasonably well in this series," said Bayliss. "In the first Test in Durban, he looked like he belonged.
"He was struggling with illness before the third Test, so hopefully he can get over that and show us what he can do in Centurion."