Darren Gough, England's leading bowler in the one-day series against South Africa, is doubtful for the final match in Centurion on Sunday.
England media manager Andrew Walpole said on Saturday that Gough had woken in the morning with a respiratory virus.
That may force England to play the wayward Steve Harmison.
Medium-pacer Alex Wharf, who took three wickets for England in the rained-out sixth one-day international in Durban on Friday, said the team had not yet been selected.
"Goughie's bowled beautifully this series and has not taken as many wickets as he's deserved," Wharf told reporters on Saturday.
"He's a quality bowler, out there with the best, and he's living proof that at 34 years old, and after a major injury, you can still come back.
"Darren used to look after me when I was a kid starting with Yorkshire and it was a good thing he took me under his wing."
Wharf played his first match of the series in Durban and took three for 48, including the wickets of Graeme Smith and Jacques Kallis with successive balls in the fourth over of the match.
"I didn't expect to play at all and I thought I was about to go home without playing a game in South Africa," he said.
"I told myself not to let the chance slip because I didn't want to go home not knowing I had given it my best go. So it was a matter of personal pride."
The 29-year-old said he was particularly pleased to get Kallis out first ball when he gloved a bouncer.
"I was pleased with my start and it was quite a bouncy pitch, so I just thought I'd let him have it and show him I'm around."
Wharf was non-committal about being the answer to England's bowling problems in the closing overs.
"I don't like to think of myself as an answer to anything, but I would like to bowl at the death," he said.
"But there should be competition for places because that brings out the best in everyone, and the selectors had their reasons for going with the others earlier in the series."
South Africa have already won the seven-match series, the abandoned match in Durban leaving them with a 3-1 lead.
England won the first match in Johannesburg and the second was tied, before South Africa won three in a row in Port Elizabeth, Cape Town and East London.
