South Africa will make a late decision on the fitness of Vernon Philander for the fourth and final Test of the series against England.
The luckless seamer was hospitalised due to a viral infection on day two of the third Test at The Oval last week, but returned to the field on Saturday.
Faf du Plessis pointed to the absence of a fully fit Philander as being a big factor in the Proteas' heavy defeat in London, but he may play no part at all at Old Trafford after suffering back spasms on the eve of the match.
Du Plessis said the tourists will have to change the balance of their side if Philander is not fully fit.
"Vernon at 100 per cent fit means we can look at playing three seamers and play seven batters," the South Africa captain said.
"Vernon at 90 per cent doesn't mean you can play three seamers because you don't want to be in a position where you have a seamer break down and then you only have two bowlers, because that is basically the Test match over right there.
"The one occasion where we managed to pull a miracle off was in Australia [last year] with two seamers, but normally you can't win a Test match with two bowlers.
"If he is not 100 per cent fit, it's important to look at having four seamers."
England take a 2-1 lead into the last match of the series, which starts on Friday.