On 4 September 2020, after his loan ended with Montpellier, Rulli agreed to a four-year deal with Villarreal. In his first season, manager Unai Emery preferred to play Sergio Asenjo in goal in the league, and Rulli in the Europa League. He made his league debut for the club on 21 April in a 2–1 loss at Deportivo Alavés, having been chosen to prepare for the European semi-final against Arsenal.