England captain Eoin Morgan is unsure of the extent of Ben Stokes' knee injury but says "a couple of days with ice on it will do him good".
Stokes - named the IPL's Most Valuable Player - appeared to be struggling during the South African innings in the first ODI between the sides and left the field for treatment following a conversation with the team doctor on the boundary.
The all-rounder returned as England stepped up their ICC Champions Trophy preparations by wrapping up a 72-run victory over the world's top ODI team at Headingley, but his fitness concerns threaten to cause a headache heading into the tournament.
"I don't know, it's in his knee, no significant swelling," said Morgan. "He was able to bowl but I didn't need him. A couple of days with ice on it will do him good.
"We want to win every game and if we can do that with all of our players fully fit, then we'll put out our strongest team every time."
Morgan, who put on 117 runs in 13.3 overs for the sixth wicket with Moeen Ali, was understandably satisfied to get the three-match series off to a winning start.
"Very pleasing, pretty good day at the office for us, having lost the toss and batted first," he added.
"The partnerships we built gave us the best opportunity to get a par score and beyond."