Spain coach Vicente del Bosque revealed the details of his conversation with Iker Casillas after picking David de Gea in goals for their Euro 2016 opener.
De Gea had been a doubt following the emergence of reports linking with him a sex scandal, claims strenuously denied by the shot-stopper.
Casillas, meanwhile, is Spain's most capped player, and had started 31 out of Spain's last 34 games at major tournaments, stretching back to the 2002 World Cup.
Del Bosque said he spoke with Casillas after the Czech Republic game - which Spain won 1-0 courtesy of a late Gerard Pique header - and heaped praise on the way the Porto goalkeeper reacted.
"When I have a doubt, I intend to choose the best. We need to manage this and there's no other choice. I've seen Casillas well on the bench and I like that," the 65-year-old told Be Mad TV.
"That Iker does not play is a pain, because I know he is a player that you really have to respect.
"Today I spoke with him because I knew it was bad to be so dry. He reacted with total normality. It's many years we have spent together.
"I don't have to show severity towards him. It was tranquil and serene. He was very understanding."'
Spain face Turkey in Nice on Friday, before wrapping up Group D against Croatia in Bordeaux next Tuesday.