The Chilean was previously in charge of Hebei China Fortune between 2016 and 2018 before joining West Ham.
According to Radio Nacional, Pellegrini has received a massive offer from a Chinese club and is considering accepting it.
The reports add that Antonio Cordon, the new sporting director at Betis, already has a contingency plan in the shape of Jordi Cruyff.
Should Pellegrini opt to go back to China, Cruyff will become Betis' new head coach.
The Dutchman was most recently in charge of the Ecuadorian national team but resigned from his post just a few days ago.