The temporary move for the Chilean international will be made permanent if Eibar stay up at the end of the season.
“The interest of the club and their sporting project attracted me,” said Orellana, who claimed to have turned down other offers.
Orellana joined Valencia at the end of the January transfer window earlier this year from Celta Vigo after a falling out with then coach Eduardo Berizzo.
However, he made just 17 appearances for Los Che and hasn’t played a single minute since Marcelino Garcia Toral took charge this season.
Orellana will have to wait until the new year to make his Eibar debut once the transfer window reopens in January.
Eibar look well set to retain their top-flight status for a fifth straight season as three consecutive wins have taken them up to 13th, seven points clear of the drop zone.
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