Sheffield United boss Chris Wilder has backed Simon Grayson to turn Sunderland's fortunes around but warned it will take more than one transfer window.
Grayson took charge at the Stadium of Light in the summer following David Moyes' resignation but after a promising start to the Championship, Sunderland have now lost three on the bounce.
The Black Cats are 20th in the table with five points from six games following the 2-1 home defeat to Sheffield United.
Blades boss Wilder says it is difficult to transform the fortunes of a club and change the culture in the space of one transfer window.
The Sunderland squad has overseen a major summer overhaul with 10 new signings and a raft of outgoings but the promise of an unbeaten start to the new campaign has quickly evaporated in recent weeks after defeats to Leeds United, Barnsley and now Sheffield United.
"It is one [transfer] window that he has worked in," said Wilder.
"Any new manager that goes into a football club will have their ideas and set ways and Simon is a very experienced, talented manager but he is working in one window.
"I imagine he will be the same, it doesn't happen overnight, trying to move players on is a massively difficult situation, especially when they are on the numbers they are possibly on here as well.
"It is really difficult to do that and change the whole team and change the culture.
"I have known Simon long enough and I know if there was someone that is going to do it - and will do it - it is him."
Sunderland have to dust themselves down quickly with Nottingham Forest the visitors to the Stadium of Light on Tuesday night, with the Black Cats desperate to end a winless streak at home that stretches back to last December.