Liverpool striker Daniel Sturridge and Arsenal midfielder Jack Wilshere both missed England's training session on Monday morning, Britain's Press Association reported.
Sturridge recently sustained a thigh injury, while Wilshere was substituted in the first half of Arsenal's 1-0 win over Tottenham Hotspur on Sunday due to stomach cramps.
Both players are nonetheless expected to remain with the squad for Friday's World Cup qualifier at home to Moldova and the trip to Ukraine four days later.
Cardiff City centre-back Steven Caulker and Spurs striker Jermain Defoe were also absent from the morning session at St George's Park in central England, but they were due to take part in light fitness exercises later in the day.
England manager Roy Hodgson has already seen three players withdraw from his squad.
Liverpool right-back Glen Johnson and Manchester United defender Phil Jones both picked up injuries during their clubs' Premier League clash on Sunday, while United striker Wayne Rooney was ruled out with a head injury.
He can nonetheless call upon Everton teenager Ross Barkley and Spurs winger Andros Townsend, who trained with the squad for the first time on Monday after being handed their first senior international call-ups.
England currently trail Montenegro by two points in European qualifying Group H, but have a game in hand.