Eagles manager Roy Hodgson told the media his glovesman was refusing to play for the club because he wants a move elsewhere.
"Sam Johnstone is the only one [first-team goalkeeper] at the moment because Guaita is disenchanted with the club and has made it clear to me and the club that he would like to move on," Hodgson said.
"He's refused to play in our games so far, but the complication is that he's got a year's contract, so it's up to the club to decide [if he will be sold] not him."
Ahead of their opening Premier League clash against Sheffield United, Palace put out their team sheet, with Sam Johnstone starting abd Remi Matthews on the bench.
Most notably, Guaita was absent from the squad.
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But despite refusing to play, the absentee Eagles star had a lot to say on Twitter when the team news was released.
"Where is my name?" the goalkeeper wrote. "So how can I play for Palace?"
Guaita made 29 appearances for the Eagles last season, making 154 for the club in total since signing in 2018.
But towards the end of the season he fell out of favour, with his last game being against Leicester at the start of April.
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The Spaniard still has one year left on his deal at Selhurst Park.