Graeme Souness, manager at St James' Park between 2004 and 2006, told Sky Sports: "I've known the situation quite intimately, I've been there, been under pressure.
"It's an intense place to be a football manager, it's everything to the people up there, and the frustrations are born from not having won anything since 1969.
"Maybe he feels a bit of bitterness towards the people, maybe he feels he should have been treated better when things were not going well."