Gerard Pique is committed to Spain and should not be doubted, international team-mate Jonathan Viera said.
Pique was jeered by fans during a training session, with the Barcelona defender criticised for his support of the Catalan independence referendum.
Viera, who was added to the squad on Monday, backed Pique and said the 91-time Spain international should be respected.
"Everybody has their thoughts and freedom of opinion. If he thinks that way, we just have to respect it," the Las Palmas attacker said.
"If he's here with us it's because he is committed to the national team.
"He's been coming for years and doing things right so we shouldn't cast doubt on him."
Viera could earn his first international cap after being called into the squad for World Cup qualifiers against Albania and Israel.
The 27-year-old said he was thrilled to be given the opportunity, one he never expected.
"The truth is that I wasn't expecting it, I'm very happy and excited to be here, I will give it all and learn a lot," Viera said.
"I've been called this morning and I was already in Madrid by chance. I'm very happy and excited to be here."
Spain are on the verge of securing their place at the 2018 World Cup, sitting three points clear atop Group G with two matches remaining.