Despite having done an impressive job at Birmingham and having the club sitting in the playoff spots in the Championship, Blues have sacked Eustace.
The Championship side have shown him the door and are widely expected to appoint Wayne Rooney as their new boss.
Hartson, who played alongside Eustace as a player, is unhappy with the way that Birmingham have shown him the door.
He dubbed Blues “despicable” and believes the sacking has left a bad taste in the mouth.
Hartson wrote on X: “I played with John Eustace at Coventry.
“Honest player and an honest man…despicable the way Birmingham have sacked him.
“Birmingham fc have said New manager to come in with a no fear style! WTF does that mean.
“Done in bad taste.”
Given the job he carried out at Birmingham, Eustace appears unlikely to have to wait long for offers to return to the game to flood in.
