The Republic of Ireland's most in-form centre-forward is now a doubt for October's World Cup qualifiers.
Manager Heimir Hallgrimsson's revealed Troy Parrott's knee ligament injury will likely put him out of the trip to Portugal and home game against Armenia.
The AZ Alkmaar striker has scored ten goals this season but is out of Saturday's meeting with Hungary and the match in Armenia on Tuesday.
Hallgrimsson has sympathy for Parrott but is confident he has good back-up at his disposal
England have added AC Milan midfielder Ruben Loftus-Cheek and Bayer Leverkusen's Jarrell Quansah to their squad for the upcoming World Cup qualifiers against Andorra and Serbia.
Loftus Cheek won his last cap seven years ago, but played under manager Thomas Tuchel at Chelsea.
Crystal Palace's Adam Wharton has withdrawn from the group because of a groin injury.
