The England goalkeeper lost his place in the City side on Saturday as manager Manuel Pellegrini decided his costly mistake in the previous week's loss at Chelsea was one error too many.
Hart could only watch as City crushed Norwich 7-0 at the Etihad Stadium, a game in which his replacement Pantilimon was hardly called into action.
On that basis it would seem harsh to axe the Romanian and so Hart may again find himself playing back-up for Tuesday's visit of CSKA Moscow in Champions League Group D.
Midfielder Fernandinho believes what has happened to Hart - hailed as the world's best just a year ago - is a strong reminder of the high standards demanded at Eastlands.
The Brazilian said: "If the quality is a bit off you must work harder to recover your position and your best quality.
"If he at the moment is not (at his best), he must work more hard.
"But they are very good keepers, he and Pantilimon. I think his career will be better for it.
"The manager must choose the best team, and the best keeper for the team.
"I am sure if he played Joe Hart or Costel Pantilimon the team would be superb because they are both very good goalkeepers."
City can all but clinch a place in the knockout stages of the Champions League for the first time by repeating their success over CSKA Moscow of a fortnight ago.
They will go into the game in good heart after sweeping the Canaries aside.
Fernandinho, signed from Shakhtar Donetsk for £30million in the summer, admitted he was surprised just how superior City were.
The 28-year-old said: "We started very well and scored four goals in the first half. The second half was very easy for us.
"Of course (I was surprised), because when I arrived here every game is hard, difficult.
"But I can only say about my team - and my team was fantastic. When they score a lot of goals I am happy."