Vicente del Bosque has insisted he left Chelsea striker Diego Costa out of the latest Spain squad due to fitness reasons rather than disciplinary concerns.
Costa, who was sent off in Chelsea's FA Cup loss to Everton on March 12 for a clash with Gareth Barry, was not included in the Spain squad for this month's friendlies with Italy and Romania.
There had been suggestions that Costa may have bitten Barry during the incident, but both the Chelsea striker and the Everton midfielder said that was not the case.
When asked if Costa would have been included in the squad had the incident not happened, Del Bosque told COPE: "No.
"I don't think so because it was not the reaction towards Barry but rather the fact that on March 9 [against Paris Saint-Germain] he got injured and had a muscular problem in his quadriceps.
"Surprisingly, three or four days later he played another game [against Everton] because it was Chelsea's last opportunity to achieve something. The [Chelsea] doctors told us that he was better and improving but we opted not to bring him."
Del Bosque said the incident that led to Costa being sent off for the first time in his Chelsea career was of serious concern.
He said: "I don't think it was that disagreeable and it's not to defend Costa at all costs, but I don't think it was that serious."
Costa's place in the squad was taken by Aritz Aduriz, who scored a hat trick in Athletic Bilbao's 4-1 win over Deportivo La Coruna on March 2 and also clinched his team's Europa League win against Valencia with an away goal in a 2-1 defeat on March 17.
The 35-year-old, whose only previous Spain cap came in 2010, has scored 17 goals and set up five more in 29 La Liga games for the Basque outfit.
"He has done enough to deserve the call-up," Del Bosque said of Aduriz. "I've always said that he is a singular case because he is 35 and because of the form he is in, but we have to remember the European championship is 10 weeks away and not 10 years from now.
"Whether Diego Costa is our striker or Aduriz, it doesn't change an idea of the play of the Seleccion."
There has been debate around the No. 9 role for some time, with Valencia's Paco Alcacer and Juventus' Alvaro Morata also vying for selection this summer.
Brazil-born Costa, who was awarded Spanish citizenship in 2013 while playing for Atletico Madrid, chose to represent Spain rather than his native country ahead the 2014 World Cup, but he has scored just once in 10 appearances for Spain.
When asked about the position, Del Bosque said: "We can take two, three or even four. We usually take three and I imagine that we will.
"There are many [candidates] and very good ones that have had great seasons. We made a forecast of Alcacer and Morata and we continue in that line.
"The criteria is that one, but we are also flexible based on what happens throughout the season."
Del Bosque, whose side will attempt to capture a third straight European crown in France this summer, knows he will face a challenging time when making the final squad decision.
"I always have a weight on my conscience when I leave out some players and bring in others," he said. "What I would not like is to leave a 'Messi' out of the squad.
"There is a lot of competition and I hope we will not make any mistake, or at least make as few as possible. Our aim is to make this call-up useful."
Del Bosque also faces the dilemma of who will start in goal, with Spain's long-serving No. 1 Iker Casillas having made several blunders recently with club Porto.
Manchester United's David De Gea is a candidate to start while Sevilla goalkeeper Sergio Rico was also included in Spain's squad for the first time in his career.
"If I haven't decided who will start [in goal] on Thursday, you can imagine about the European Championship," Del Bosque said. "We will see.
"I have confidence in our two goalkeepers, in fact in our three, with Sergio Rico here. Rico is good and we will see if he can make his debut.
"It's impossible that goalkeepers don't make mistakes."
Spain travel to Udine to face Italy for their friendly on Thursday and then go to Cluj in Romania three days later.