Manchester City manager
Former Manchester United midfielder
Keane's comments came as the television station filled time after the kick-off for Tuesday's game in
His remarks also came in spite of a performance against Borussia Dortmund earlier in the month after which Hart was widely hailed as the best keeper in the world.
But the 25-year-old was at fault as
When asked about Keane's comments, Mancini said: "Every keeper is like this.
"It is important because if not, you should choose another position. If you want to be a keeper you should be cocky.
"Joe is a good guy, he works very hard for this, he wants to improve.
"Remember last week, (
"It is my opinion
Keane suggested that Hart was not facing enough competition for his place with club or country and may therefore take "his eye off the ball".
"There's a fine line between confident and cocky, and I think he's been a little bit too cocky this year," said the Irishman.
Mancini dismissed those concerns, even though Hart has only kept one clean sheet for City this season.
The Italian said: "Joe is strong enough for this. He knows he is one of the best but if you want to continue to be the best you should work very hard.
"Everyone can make a mistake, it is impossible to be perfect. Only Mario (Balotelli) is perfect every day!"
The postponement of the England match meant a disruption to Mancini's preparations for the champion's English Premier League match at West Bromwich Albion this weekend.
As well as Hart, defender Joleon Lescott and midfielder
It was a freak disruption but even though Mancini did not necessarily want City's trip to The Hawthorns put back as a result, he thinks there should be flexibility for that to happen.
He said: "I think sometimes when this situation happens we can move our game from Saturday to Sunday. This is easy because we are not on TV and we play at three o'clock Saturday.
"But I am not disappointed. I am worried because Joe, James, Joleon - today (Friday) is the first day training and we play tomorrow."
There were reports that some England players took sleeping pills after the postponement on Tuesday to help them rest ahead of the rearranged game.
It has also been claimed that some caffeine tablets were taken prior to the match the following day.
Mancini does not think that is an issue.
He said: "If there are some players that want to take a coffee he can.
"I don't think you need to take a pill to sleep but I know nothing. No player ever talked to me about this."
English Premier League