Skipper Andrew Strauss and spinner Graeme Swann missed a practice session on Tuesday due to stomach upsets only two days before England's crucial, must-win World Cup match against the West Indies.
Strauss and Swann weren't able to practice in the morning, but an England team spokesman told reporters that both players were expected to recover before Thursday's Group B match at Chennai.
Following upset losses to Ireland and Bangladesh, England will be eliminated in the first round unless it beats the West Indies. It means England must be at full strength and can ill afford to lose either of the key players for the clash.
Despite his good form with the bat, Strauss is under intense scrutiny for his leadership in an inconsistent campaign that has included an impressive comeback win over South Africa, a high-scoring tie against India and the two losses to lower-ranked teams.
Swann was also in trouble for an expletive-laden outburst during the loss to Bangladesh in Chittagong last Friday, for which he was fined 10 percent of his match fee.
Even a win over the West Indies won't guarantee England a place in the knockout round, with Bangladesh and South Africa still to play after that.
But in an interview Monday, Swann was confident England could advance.
"We play our best cricket when we've got our backs against the wall," he said.