Onda Cero says Villarreal are moving for Marin as they seek a replacement for departing veteran defender Raul Albiol.
Marin, formerly of Real Madrid, has already agreed personal terms with Villarreal.
The Yellow Submarine are now in talks with Napoli over a loan-to-buy arrangement for the Spanish youngster.
Villarreal have moved quickly knowing they need an extended squad given their Champions League qualification for next season.