Roy Hodgson says England did not hesitate to send Theo Walcott home after he was violently ill on Sunday night, but he is hopeful Daniel Sturridge will still be available for the game against Ukraine.
Walcott and Sturridge both missed training on Monday after feeling unwell and the Arsenal man was then ruled out of the squad as he was too poorly to be considered for Tuesday's clash at Wembley.
Hodgson hopes the rest of his players will stay healthy and is also optimistic that Sturridge will recover, although he has called up Raheem Sterling, Adam Lallana and Jake Livermore as cover.
"Theo has picked up some sort of virus," said the England manager. "He was quite violently ill last night.
"Daniel trained yesterday with stomach cramps but today woke up with the same stomach cramps, and the doctor advised us to keep him out of training and see how things are. The doctor is quite confident he will be okay, though.
"I can only hope nothing is going round the squad. That was why we were quite keen to get Theo home as soon as possible and also keep Daniel away from the squad.
"I have to hope it's just an isolated case with the two players."
Hodgson believes the chance to work with the senior squad will provide Sterling, Livermore and Lallana with valuable experience.
"It was a good opportunity to invite some young players to come in and be part of the atmosphere," he said.
"We still have enough good players to be able to deal with the game, but it's always good when you have the chance to invite these players to come in and see how things are."