England manager Roy Hodgson admits he may have to rotate his side for Friday's Group D match with Sweden.
Hodgson has concerns over the fitness of Scott Parker and Steven Gerrard after Monday's 1-1 draw with France.
"I will have to assess the freshness of my team and see whether they are able to do that again," said Hodgson.
"Scott Parker and Steven Gerrard are both over 30 and had to work really hard. I'm not the only coach wondering 'can they do it every four days?'"
Tottenham's Parker, 31, has been nursing an Achilles tendon, while there are concerns over 32-year-old Gerrard's ability to play two games in the space of four days, particularly in the energy sapping heat England experienced in Donetsk on Monday.
Liverpool's Jordan Henderson was a late substitute against France, while Manchester City's James Milner could also play in the middle after starting wide on the right in Donetsk.
Whoever he asks to play against Sweden, Hodgson is confident he has a squad that is in good form and capable of getting a result.
"My gut feeling, after a good recovery day on Tuesday, a sensible training day on Wednesday and sensible recovery day on Thursday, is that it will be very hard for me to leave people out," he said.
"If we said 'we're going to give you a rest because it's too much to play two games in four days,' some of them would have us up against the wall.
"But what we've got to make certain of, is that if they can't, or start to show signs of fatigue, that others are ready to go in and do exactly the same job.
"The mood in the dressing room is exceptionally good because we have shown we can handle difficult conditions, against a France team of that quality, and come away with a good result."
A win against Sweden - who England beat for the first time since 1968 last year - would leave Hodgson's side in good shape to qualify for the last eight with a result in their final group game against co-hosts Ukraine on 19 June.