Aston Villa midfielder Jack Grealish was called up to the England squad on Monday for the first time as a replacement for the injured Marcus Rashford.
Grealish was not named by manager Gareth Southgate in the initial squad despite helping lift Villa out of the relegation zone with eight goals and six assists last season.
Manchester United forward Rashford withdrew as he continues to recover from an ankle injury.
"Gutted... never want to let this team down but these fixtures just came a little too soon for me," Rashford wrote on Twitter.
"I tried my best but I have to focus on starting the season at my strongest for club and country."
Tottenham Hotspur midfielder Harry Winks is also unavailable.
"Without Rashford and Winks and following the addition of Conor Coady and Ainsley Maitland-Niles, the England manager will now begin his preparations with a squad of 24," the FA said in a statement.
England travel to Reykjavik to play Iceland in their Uefa Nations League group opener on Saturday before facing Denmark in Copenhagen three days later.