Jofra Archer, Stuart Broad and Jack Leach all remain a doubt for England's final warm-up match against South Africa A at Benoni, starting on Friday, leaving the squad's plans for next week's Boxing Day Test in some disarray.

All three players were forced to sit out the low-key tour opener against a South Africa Invitational XI earlier this week, after a bug swept through the England camp, and according to an ECB spokesman, their fitness for this weekend's three-day fixture won't be confirmed until the morning of the match.

Unlike the opening match, the South Africa A game is a designated first-class fixture, featuring a strong opposition including regular Test-squad members Temba Bavuma, Theunis de Bruyn and Andile Phehlukwayo.

Therefore, England will be unable to substitute the trio into the line-up should they recover later in the contest, meaning that those players risk going into the first Test at Centurion with no match practice in South African conditions.

Speaking at the conclusion of the two-day game on Wednesday, Chris Woakes acknowledged the sickness in the England camp.

"A few guys have gone down a little bit ill, so obviously they're back in the hotel trying to steer clear of everyone," he said. "Hopefully it's not too bad, hopefully it'll be a couple of days out and they'll be back on their feet."

While the timing of the illness is not ideal for the squad as a whole, it is particularly problematic for Leach, who was omitted from England's most recent Test, against New Zealand in Hamilton last month, and then suffered a bout of gastroenteritis that would have ruled him out for much of the game anyway.

In his absence, England gave an outing to the legspinner Matt Parkinson in their opening tour game in South Africa, but he endured some rough treatment as Joe Root emerged as the most economical spinner on the day.

With a range of allrounders in England's squad, including Ben Stokes, Sam Curran and Chris Woakes - all of whom are currently fit for selection - England could yet decide to take the field in Centurion without a frontline spinner for the second Test in a row, especially at a venue that has traditionally favoured seam bowling.

Assuming he is fit in time for the Centurion Test, Archer seems guaranteed to take his place in England's starting XI - even though he endured a tricky first taste of overseas Test cricket in New Zealand, claiming two wickets at 104.50 in the series.

Broad, however, would doubtless benefit from time in the middle as he seeks to build on a decent display in New Zealand, where he was England's most penetrative bowler on a flat deck in the first Test at Mount Maunganui. However, he had been omitted from three of England's previous six overseas Tests in Sri Lanka and West Indies, amid doubts about his penetration with the Kookaburra ball.

England also face a tricky decision over the fitness of James Anderson, who came through 11 overs unscathed in Benoni, but whose recent injury record invites caution at the start of a four-match series. He broke down after four overs of the first Test against Australia in August, and did not feature again in the series.

© ESPN Sports Media Ltd.