Villarreal were humbled 2-0 at home by third-tier Mirandes in the King's Cup on Wednesday, losing the last-32 tie 3-1 on aggregate and prompting president Fernando Roig to sack Garrido immediately after the final whistle.
He leaves the side hovering just above the La Liga relegation places after 16 rounds of a stuttering campaign that also saw them beaten in all six of their Champions League Group A games, scoring just two goals and conceding 14.
Molina, 41, who kept goal for Villarreal, Atletico Madrid and Deportivo La Coruna, has agreed a contract until the end of the season, the club said on their website.
He joined the staff in the 2009/10 campaign as C team coach and helped the B team avoid relegation last season when he took the helm with four matches remaining.
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