Leeds United initially signed Pablo Hernández on a loan deal from Qatari side Al-Arabi in the summer of 2016 before making his move permanent in January 2017.
The 34-year-old has since signed two contract extensions at Elland Road and his current deal expires at the end of this season.
Earlier reports in England indicated the Whites have an option to extend the contract further by a year if they achieve promotion to the Premier League.
There have also been suggestions Marcelo Bielsa’s side are set to hold talks over extending the winger’s stay at the club.
Hernández spent time at Valencia’s academy and before joining them, he was at CD Castellón for six years between 1997 and 2003. The latter are currently plying their trade in the third division of Spanish football.
Castellón are looking to increase the number of season ticket holders and on Wednesday they reached a milestone of 13,500 subscribers.
Hernández has now opened the door to play for his former club again and finish his playing career where he started, according to La Vanguardia.
“ CD Castellón is a unique club and I hope to take the albinegra again very soon and return to Castalia,” he said.