Simon Grayson lasted just four months in charge at Sunderland.
Former Sunderland manager Simon Grayson has told Sky Sports' EFL Matters that the deep-seeded mentality of his old side is what is dragging them down and claimed it was ultimately the downfall of his reign.
Grayson, 47, took over at the Stadium of Light with optimism surrounding his appointment following past promotions with Leeds United, Blackpool and Huddersfield Town, following Sunderland's relegation to the Championship.
However, Grayson was unable to shake off the lingering smell of defeat around the Wearside club, which saw him sacked on October 31 with the club rock bottom of the Championship table.
Chris Coleman has since replaced Grayson and earned Sunderland's second win all season against Burton Albion on Saturday, but Grayson believes the problem with the squad's mentality will continue to exist as seven or eight players are still suffering.
"I think we had a good squad, it was more of a mental issue with some of the players," Grayson said. "One of the problems at Sunderland is that there are seven or eight of them who are still suffering the consequences of what has happened over the past two or three years.
"They need to overcome that hurdle in order to turn the negativity into positivity. The new players were fine because they were not having to carry that baggage with them. But as the results continued, they got dragged into that negativity that was around the place.
"Eradicating that mental hangover for an individual is difficult. If you are trying to do that with seven or eight players it is a really tough task."
The likes of John O'Shea, Lamine Kone, Lee Cattermole, Billy Jones, Jack Rodwell, Duncan Watmore and many more are still in the Sunderland squad after suffering relegation to England's second tier.
Former Wales boss will be looking to continue his strong start to life with the Wearside club as Sunderland go up against Reading on Saturday afternoon, as they look to capitalise on the Royals faltering 2017-18 campaign.
Three points for Sunderland would see Coleman take the club out of the bottom three and into 21st place, with Birmingham facing Midlands rivals Wolves on Monday night.