Daniel Sturridge and Jack Wilshere both missed England training on Tuesday morning as the squad gathered to prepare for the upcoming World Cup qualifiers against Moldova and Ukraine.
Sturridge was carrying a thigh injury during Liverpool's victory over Manchester United and has been given extra time to get back to full fitness.
Wilshere went off in the first half of Arsenal's win against Tottenham at the weekend with stomach cramps and he has also been afforded more time to try to recover.
Both players will remain with the squad at St George's Park, though, and the hope is that they will be fit for Friday's qualifier against Moldova and the crucial game in Ukraine four days later.
England manager Roy Hodgson is desperate for the in-form Sturridge to be fit for the double-header as he is without leading striker Wayne Rooney, who withdrew at the weekend with a head injury.
Cardiff defender Steven Caulker and Tottenham striker Jermain Defoe did not train with the England squad in Burton, but they will do light fitness work later in the day.
All the other members of Hodgson's 25-man squad trained at the national football centre, including Ross Barkley and Andros Townsend, who have been called up for the first time.
Hodgson's preparations for the crucial games suffered a blow last weekend when Rooney, Phil Jones and Glen Johnson pulled out through injury.
Speaking during an afternoon press conference, Theo Walcott was not overly concerned by the absence of Sturridge and his Arsenal team-mate Wilshere.
"He (Sturridge) is here - that is the positive," he said.
"Hopefully Dan can get over the knock.
"He played with it (on Sunday) I think so fingers crossed he will be okay for Friday and Tuesday.''
Of his Gunners team-mate Wilshere, Walcott added: "He's had an illness so he needs an extra couple of days to recover.
"I am sure he will be fine, hopefully.''