Arsenal defender Gibbs would have been England's first choice left-back but he was unable to fly with the majority of the squad to Denmark yesterday because of an ankle problem.
No go: Arsenal left back Kieran Gibbs (left) is nursing an ankle injury and so will not travel to Denmark
Pearce will now be faced with the choice of using Chelsea's Ryan Bertrand in that position for Sunday's Group B opener against Spain or bringing Tottenham's Danny Rose in.
England are unable to call up a replacement at this late stage after submitting their definitive 23-man squad list to UEFA on June 1.
But the head coach - who has already lost Gibb's Arsenal team-mate Jack Wilshere, Liverpool striker Andy Carroll and Manchester City's Micah Richards in the build-up - is refusing to get flustered.
'We have had to deal with setbacks every now and again,' said Pearce. 'But we are fortunate to have a squad and staff with previous tournament experience. It is unfortunate for Kieran but he went for a scan and is now in a medical boot.'
End of season: Jack Wilshere pulled out of the U21 European Championships but played for England last week
Young Lions: Gibbs is already a full international as is Andy Carroll (right), who also dodged the U21 squad
There is already a sense that Englandwill be on the back foot when they play a Spain team in Herning that islikely to include Manchester United target David de Gea and Valencia's Juan Mata.
However, United striker Danny Welbeckis not daunted by the prospect and has warned Spain it would be foolishto underestimate England.
'Spain are a good team but we are going to give it a good shot,' said Welbeck. 'They will have players in our team who they will fear, so it should be a good game.
'I'm looking forward to it. We have got a really good squad. Everyone is young, hungry and eager to improve.We want to be winners.'
Protective: Arsenal boss Arsene Wenger (left) insisted Wilshere was too tired to play this summer
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Explore more:People: Stuart Pearce, Ryan Bertrand, Andy Carroll, Jack Wilshere Places: United Kingdom, Norway, Denmark, Spain, Czech Republic