Garcia was stretchered off in the 80th minute following an accidental clash with his team-mate, as City’s Premier League campaign resumed with a comprehensive victory.
The two collided after the Brazilian goalkeeper came racing off his line to make a clearance.
The 19-year-old defender came off worse, suffering a head injury and, after a lengthy stoppage, he left the field and was taken to hospital.
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“We are concerned about Eric, of course,” said Guardiola afterwards.
“He is conscious, but he is going to be tested tonight because a kick in the head is always so dangerous.
“I am pretty sure we are going to do absolutely everything to be sure that Eric feels fine. I think after what happened, he may be in the hospital for one or two nights.
“We are going to make sure everything is fine for him.”
Prior to the injury, Garcia had produced a composed display to keep the Arsenal attack at bay in just his third Premier League start.
With a full squad of senior players to choose from, the youngster’s inclusion raised eyebrows before kick-off, but Guardiola says the Spaniard’s understanding of the game and unflappable nature, mean he has no doubts about his ability to perform in the first team.
“Eric came back incredibly well,” added the City boss.
“He is so intelligent to guide the line. It was not easy to play against Aubameyang. He is training really well and we tried to work with Juanma and Rodolfo in this period.
“He understands perfectly well. This season, especially in the winter time, he always played good. He doesn’t make mistakes. He is always focused.
“In this game, we knew we were playing dynamic players. He understands the position and the movement.
"Against Burnley, for example, they play more long balls and we might need another kind of player.
“For this game, we thought he was the right guy to play alongside Laporte and they played really good.”
Guardiola also reinforced his support for the Black Lives Matter movement, saying he is ashamed of the racism which has existed for centuries.
Players and staff from both City and Arsenal made a powerful statement by taking a knee immediately before kick-off at the Etihad and the boss insists more needs to be done to fight racism.
“What we should say as white people, is sorry,” he said.
“The way we have treated black people in the last 400 hundred years, I feel ashamed. What we have done is marvellous for black people around the world.
“It is not just a problem in the US, with what happened with Mr Floyd. Racism is a problem everywhere.
“Maybe our generation is too late, but hopefully the new generation can understand that we are all human beings.
“Every gesture is important, but it is a fight, day by day. It is a problem from a long time ago and we have to support it day by day."