England head coach Trevor Bayliss admits James Anderson's fitness is a worry ahead of the Boxing Day Test against South Africa.
Anderson had scans on his right calf in Pietermaritzburg on Tuesday having experienced discomfort and tightness for the past week.
The 33-year-old, England's leading Test wicket-taker, is crucial to the touring side's prospects in the four-match series and will be waiting nervously for the results, which have been sent back to England for analysis.
He has bowled just five competitive overs on tour and played no part in the final thee-day warm-up against South Africa A, leaving a maximum of two net sessions - on Christmas Eve and Christmas Day - to get back up to speed.
"Unfortunately Jimmy's had a little bit of a tight calf muscle. We're just waiting on some test results there and hopefully we'll know in the next day or two," said Bayliss.
"It's a concern. He hasn't been able to bowl a lot of overs on this tour...he has bowled overs though so whatever it is it's not a terribly bad one."
With just two days between the first and second Tests, one of which involves travelling from Durban to Cape Town, Anderson would seem a long shot to feature in both.
England are increasingly mindful of his workload and may blanch at the prospect of committing him to the possibility of 10 days cricket out of 12.
But, as Bayliss was keen to point out, they have coped without their leading light emphatically in the recent past.
When a side injury ruled him out of the decisive Ashes Test at Trent Bridge in August, Stuart Broad shouldered the responsibility in stunning fashion on his way to career-best figures of eight for 15.
Australia were bundled out for an embarrassing 60, the urn was secured and fears over an Anderson-less attack swiftly dissipated.
"It's always a concern if your leading bowler or leading batter misses a game but the last time he missed one we did pretty well so you never know," said Australian Bayliss.
Chris Woakes is on standby to replace Anderson, having impressed with both his pace and control in the early stages of the tour.
Uncapped left-armer Mark Footitt would offer variety but after a nervy showing against an Invitational XI in Potchefstroom and a brief bout of cramp in Pietermaritzburg, would represent a risk.