England U21 coach Gareth Southgate says he left Tottenham defender Eric Dier out of his squad after a "mature chat".
Dier is focusing on being a centre-half.
"It is an interesting one. We had quite a mature conversation about it," said Southgate, who was at pains to stress Dier has not snubbed the Under-21s and would have been prepared to play right-back if called upon.
"Long-term we both agree that he is unlikely to be a full-back but he is still happy to play there.
"He is going to be a centre-back. And, without wishing Mauricio a problem, I think I agree with that.
"Let's be clear about this. He feels there's benefit to working on that with time on the training during this period. Here, we're preparing for a game. In development terms, back at his club, the footwork training, the mobility training, you can do a lot more of that if you're not working towards a game.
"So we agreed, that with him having played the last two for us, we didn't need to see him, he would go through that work.
"Will there be a black mark? No. I'm sure if I had picked him he would have come at right-back or wherever.
"I've had other scenarios where people have elected not to come. And they're not here. But this is different. I'm totally comfortable with this."
