Hartson played for Hughes with Wales and said: "It's ridiculous to say he is under pressure 12 games into a season.
"I know he has spent a lot of money, but what do people expect?
"Do people really expect Manchester City to have won 12 out of 12?
"Mark has a job to do and he is trying to win football matches and he is working extremely hard to get it right.
"This is all new to him as well remember.
"I know Mark has played at a great level in his life, but he has never been under this sort of scrutiny as a manager."