Vicente del Bosque says he has been force to excluded some important players, including Manchester United playmaker Juan Mata and Chelsea's full-back Cesar Azpilicueta, from his latest squad due to the high competence in their positions.
The Premier League duo played the World Cup but has since fell out of favour of the Spanish manager ahead of other players.
Mata, who has struggled to earn a regular place at Old Trafford under manager Louis van Gaal, has been excluded from Del Bosque's plans since the disappointing 2014 World Cup campaign, when Spain were surprisingly knocked out in the group stages.
Meanwhile, Azpilicueta was included in the Spain's squad earlier this season but was an unused substitute in the European Championship qualifiers against Macedonia, Slovakia, Luxembourg and Belarus.
Del Bosque has left both players out of the squad for the upcoming games against Ukraine and the Netherlands.
The Spain manager has included four other full-backs ahead of Azpilicueta in Barcelona star Jordi Alba, Bayern Munich's Juan Bernat, Atletico Madrid's Juanfran and Real Madrid's Dani Carvajal.
And he opted to leave Mata out of the squad to make way for Andres Iniesta, Santi Cazorla, David Silva, Pedro, Koke, Isco and Sevilla winger Vitolo.
The manager has suggested he still have the duo in mind but says there is not space for everyone, as he has also been forced to forget the likes of Rayo Vallecano striker Alberto Bueno, who was expected to be in his squad after scoring 15 La Liga goals this season.
"All the players who have come deserve it. Bueno and Mata have not been included because they have to compete for a place with the playmakers that we already have. It is not a decision on a whim. We are not here to give prizes to anyone but to bring the best players to try to win Ukraine. We try to bring the best players and the ones who give us more solutions," Del Bosque said to Onda Cero while explaining why he has call up Malaga forward Juanmi to replace injured Diego Costa.
While speaking about Azpilicueta, he said: "We miss him because he has had always a fantastic behaviour but this time we have opted to use other full-backs."
Nevertheless, the manager has insisted that he always try to monitor the players who are not playing in La Liga, revealing he thought about bringing in Newcastle United striker Ayoze Perez to replace the injured Diego Costa.
He said: "We have proved that we treat the migrants well. If this time we have not brought them is because we opted for other. But we have considered players like Newcastle's Ayoze or Salzburg Jonathan Soriano when we had to find a replacement for Costa."