The Blues midfielder spent the second half of the 2019/20 campaign with the Spanish side who eventually finished in fourth place at the resumption of football after the lockdown.
He will be looking to add to the two goals and two assists in his 18 appearances for the Andalusian side, who narrowly missed out on promotion in the play-offs.
Villalba became a Blues player in August 2019 after joining from Spanish side Valencia on a three-year contract.
Prior to moving back to his home country at the start of the year, the 22-year old made 17 appearances and scored one goal for Blues.
His last appearance in royal blue came in the 3-0 defeat away at Hull City in December 2019.