Athletic Bilbao have reached an agreement in principle to appoint Marcelino as coach until 2022 after sacking Gaizka Garitano.
The LaLiga club sacked Garitano, who took charge in December 2018, just hours after recording a 1-0 win over Elche on Sunday.
That result sees Athletic sitting ninth in the table, seven points adrift of fifth-placed Barcelona.
Former Valencia boss Marcelino was announced as Garitano's replacement later on Sunday.
Athletic announced they had reached an agreement in principle with Marcelino until 2022.
After more than two years in charge, Marcelino was sacked by Valencia in September 2019.
He helped the LaLiga club win the Copa del Rey in 2018-19.