Spain coach Luis Enrique refused to answer questions regarding his continued omission of Barcelona left-back Jordi Alba from the national squad, but said his decisions are based purely on sporting reasons.
A regular under Luis Enrique's predecessor Julen Lopetegui and a starter at the World Cup in Russia, Alba assisted three goals in Barca's 4-2 win over Tottenham on Wednesday.
Left out of Luis Enrique's first squad selection, he has again not been included by his former Barca boss for upcoming games against Wales and England, with reports in Spain saying he fell out of favour with the coach during their time at the Nou Camp.
"By rule, I don't talk about players who are not on the list," Luis Enrique said at Thursday's news conference. "But I've always left out players based on sporting reasons. Unfortunately, I can only bring 23 players knowing that there are another 20 players that could play and do well for the national team."
Borussia Dortmund's in-form striker Paco Alcacer has been included in the squad for the first time since March 2016.
Alcacer has scored four goals, including his team's second in a 3-0 win over Monaco in Wednesday's Champions League, in three games since joining Dortmund on loan from Barcelona this summer.
"I know Paco well," Luis Enrique said. "He had a brilliant spell at Valencia. He had limited time with us at Barca. Although I tried to give him some playing time it was not possible.
"Now at Dortmund, he is playing well, he is scoring goals. With some players out injured, I'm thrilled he can be with us."
Atletico Madrid midfielder Koke, who also played at the World Cup but did not make Luis Enrique's first list, is back.
Spain will be without Real Madrid midfielder Isco, who is recovering from appendicitis, as well as Dani Carvajal, Inigo Martinez, Sergi Roberto and Diego Costa who are also injured.
"Isco's absence is difficult to deal with," Luis Enrique said. "He is a key player, dominating. There is no one like him but there are players with different characteristics and qualities that can cover that role.
"I think it's a good opportunity to see other players, to bring competition and not fall asleep. I try to look at the positives knowing that injuries are something negative."
With Carvajal and Martinez out, Luis Enrique has called up Wolverhampton Wanderers right-back Jonny Otto, who has yet to make his senior debut and is one of six Premier League based players included in the squad.
"Otto played many games as a right back last season although now he is playing as a left back," Luis Enrique said.
Real Betis defender Marc Bartra returns to the squad, earning his first call up under Luis Enrique.
Chelsea and Real Madrid are the clubs with the most players in the squad with four each, as Luis Enrique continues to place his trust in Alvaro Morata despite the forward's slow start to the campaign with just one goal scored.
Luis Enrique said that Morata may not even feature for Spain in this round of fixtures after a quiet month at Chelsea.
"He didn't play last month and I don't know, it may or may not happen," he said. "The game against Wales allows me to test players but we want to continue to win. The key game is the one against England."
Spain have won their opening two UEFA Nations League Group 4 games, scoring eight goals and conceding one.