Former Sunderland manager Gus Poyet believes managers are not to blame for the club's woes, while he endorsed Sam Allardyce for the vacant role.
Dick Advocaat quit last week with Sunderland languishing second-from-bottom in the Premier League.
A number of candidates have reportedly turned down the chance to join the club, Real Sociedad boss David Moyes believed to be among the list, as Sunderland search for their fifth manager since 2013.
Poyet, though, feels the problems lie much deeper than the coaching staff.
"Sometimes when a team is not working you change the manager and things go well and you can say good decision but when it happens four or five times? Come on, be realistic now," said Poyet, who was sacked in March.
"I don't think you can blame Martin O'Neill, Paolo Di Canio, myself and Dick Advocaat.
"There is something that is not working there and it’s clear that what everybody was naturally accepting, that it was the manager, is not [true].
"They need to make an appointment now and stick with whatever results come in the next two or three years.
"That would be my very humble advice, not to give the chance to someone until the end of the season.”
Former West Ham manager Allardyce is tipped to take over, as long as the club heeds to his financial demands.
Poyet added: "[Allardyce] knows the Premier League inside out and he knows exactly what a team needs to do to stay in the Premier League.
"He has done it everywhere he has been so it’s not something new. That experience of being there for so long will definitely help."
