The former Magpies bosses are bitterly disappointed with proceedings at St James' Park.
During the Tyneside outfit's humiliation at the hands of Manchester City at the weekend, Gary Lineker revealed the extent of Shearer's frustration on social media.
And, in the wake of that loss, Shearer has now expressed his disappointment at the approach Newcastle took in the FA Cup this term - a competition in which he feels the St James' Park outfit missed a trick.
“[They are] hopeless in the cups and around 10, 11, or 12th in the league," he told the Chronicle.
“However, it’s the attitude to the FA Cup that particularly annoys me. United go out at bottom-of-the-league Leicester but look at the quarter-finals."
On their 5-0 defeat to Manchester City, meanwhile, Shearer added: “They were pathetic, embarrassing. It was all far too easy for City. Newcastle never got near them. They didn’t fancy it. It beggars belief. A real horror show.”
Meanwhile, former Newcastle boss Keegan shared those sentiments, fearing the club are going in no specific direction with regards to the long term.
“It hurts me to say it but Newcastle are a club going nowhere," Keegan said on beIN Sports.
Newcastle host Aston Villa in their next Premier League clash this Saturday afternoon and a win would do boss John Carver the world of good.
The 50-year-old has won just once as Newcastle boss and faith in him appears as though it could not be lower after the Magpies' miserable showing at Manchester City.