Sam Allardyce says Sunderland must go for an experienced manager to 'stop the rot' - and says Simon Grayson was 'perfect' for the job.
The former Black Cats boss, who quit the club in July 2016 to take over at England, believes whoever takes on the role has a huge job on their hands.
LIVE: Sunderland close in on new manager - updates here
Grayson was sacked more than two weeks ago, just four months and 15 league games into his tenure.
Having been lured away from Preston North End because of his Championship pedigree, Grayson was seen as the ideal man to help Sunderland stabilise after relegation from the Premier League under David Moyes.
However, Sunderland's woes continued with just one win under the new manager, and he paid the price, being sacked after a 3-3 draw with felow strugglers Bolton Wanderers left the club bottom of the Championship.
The search for his replacement continues, with relative rookie Paul Heckingbottom the favourite to be appointed, while chief executive Martin Bain is also considering Northern Ireland's Michael O'Neill, ex-Middlesbrough manager Aitor Karanka, and former Rangers boss Ally McCoist.
When asked what type of manager Sunderland should go for, Allardyce said: "I thought they had it. Simon Grayson is an outstanding manager.
"What he's done for most clubs, and certainly what he was doing at Preston last season, he was working on one of the slimmest budgets in that league.
"It was probably in the bottom four or five in terms of total budgets and he had them in the top half and nearly in the play-offs.
"I thought he was the perfect choice.
"Unfortunately, the rot must have set in at Sunderland and when you go into a relegated club, and I had experience at West Ham, it's one hell of a job.
"You have so many disgruntled players, staff have been let go and made redundant, the place is on its knees and it takes something really special to revive it and get it going in the first season.
"That was certainly his (Grayson's) biggest problem. Players not performing to the level they can, players getting sold on or pushed out on loan on bigger wages.
"The club really needs a manager now with great experience to pull that all together and get a team playing and functioning, and make sure they don't get relegated again."