Southampton left-back Ryan Bertrand withdrew on Thursday, while Theo Walcott is a doubt after suffering a dead leg.
England face the Netherlands at Wembley on Tuesday.
With Hart absent, manager Roy Hodgson confirmed that understudies Jack Butland and Fraser Forster will each play in one of the two friendlies, but did not state which of the two would feature in Germany.
The fixtures form part of the Three Lions’ preparations for Euro 2016, with games against Turkey, Australia and Portugal to follow in May and June.
Hodgson, who is leading England into a third major tournament, said: “I’m confident that the team I’ve selected is a good team to take on the might of Germany.
“These matches will be very important occasions and there’s no doubt what I’ve seen in training this week and what I see in these games will have an impact [on the make-up of the final 23-man squad for the Euros]. It’s by no means a be-all and end-all situation but we are taking the games very seriously.
“I can’t absolutely guarantee every single player will feature in the two matches but our intention is to use the whole squad to look at people and give them the chance to impress.”
Goalkeepers: Jack Butland (Stoke City), Fraser Forster (Southampton), Tom Heaton (Burnley).
Defenders: Gary Cahill (Chelsea), Nathaniel Clyne (Liverpool), Phil Jagielka (Everton), Danny Rose (Tottenham Hotspur), Chris Smalling (Manchester United), John Stones (Everton), Kyle Walker (Tottenham Hotspur).
Midfielders: Dele Alli (Tottenham Hotspur), Ross Barkley (Everton), Eric Dier (Tottenham Hotspur), Danny Drinkwater (Leicester City), Jordan Henderson (Liverpool), Adam Lallana (Liverpool), James Milner (Liverpool).
Forwards: Harry Kane (Tottenham Hotspur), Daniel Sturridge (Liverpool), Jamie Vardy (Leicester City), Theo Walcott (Arsenal), Danny Welbeck (Arsenal).