Gareth Southgate believes England's squad men could be vitally important this summer as they can 'ruin it' if their attitude isn't right.
Jordan Henderson could become the latest player from Roy Hodgson's standby list to be called up to the full squad if Frank Lampard fails to recover from a thigh injury picked up in training.
Phil Jagielka has already been added to the 23-man Euro 2012 party after Gareth Barry was forced to withdraw with an abdominal problem, while young goalkeeper Jack Butland came in for third-choice goalkeeper John Ruddy.
The changes have brought into sharp focus the apparent decision of Micah Richards to refuse a standby berth and Michael Carrick's request not to be considered if he was set to sit on the bench.
While Southgate respects that view, the FA's head of elite development believes that if you want a successful England career then making the sacrifices can pay off.
"I think every player has to do what is right for them," Southgate told Sky Sports on Wednesday, when he was taking a training session for the Carlsberg Pub Cup champions in Eltham.
Hang in there
"I'm delighted for Phil (Jagielka) because he was on standby and if you want to be involved with England you have to hang in there sometimes.
"I remember the World Cup in 2002 and Trevor Sinclair was flying back from Japan. Danny Murphy got injured in a training session and Trevor flew back out.
"I know that he then played in the game against Argentina when we won 1-0 so it was a brilliant experience for him."
Southgate has experienced both sides of the coin at European Championships for England.
In 1996 he may have missed the crucial penalty against Germany in the semi-final, but Southgate did not miss a single minute of England's impressive campaign on home soil.
Four years later in the Low Countries and the then Aston Villa defender had a watching brief for all but 10 minutes of England's unsuccessful tournament as they were eliminated at the group stage.
And he admits that can be a tough experience, which is why it is even more important that the squad players want to be there.
Southgate added: "It's not easy as you spend your whole life preparing to be a player.
"When you are with your club you are a first choice for your side so it's difficult to handle.
"But you've got to make sure that you are a positive member of the group because players that aren't in the side can ruin it if their attitude and approach isn't right.
"That's something we're quick to tell people that go with our junior national teams. They've got to make sure that training is competitive and that their body language is supportive of the team.
"They may be going in at any time and they've got to be ready for that. The success of the team is everything so you've got to put your own feelings to one side."