For the first time in three years, Hart's position as England's number one has come in to question after a series of sub-par performances for club and country.
But, to Hart's credit, he has not ducked the issue since joining up with the England squad in Burton.
"Joe has been his bubbly self," the Everton defender said. "Joe wouldn't want to tiptoe around the issue, he loves the banter more than anyone.
"You just throw the odd comment in. You're losing 10-9 to him at table tennis and I'm waiting for the next point, and you just say 'Bayern Munich' or something.
"That's just the kind of thing you do.
"He gave me some back because City beat us 3-1 at the weekend so I didn't have a leg to stand on.
"Joe's a great guy and a fantastic goalkeeper and if he can take it like he has done all the power to him."
Hart will have to be at his best on Friday when England host Montenegro and then again four days later for the visit of Poland.
As it stands, the only way Hart and his team-mates are guaranteed to be on their way to Brazil next summer is if they win both games at Wembley.
Jagielka will line up in front of the Manchester City man he has no doubt about the 26-year-old's ability to perform under the microscope.
"There is no question in my mind how Joe will react and how he will perform," he said.
"He is a fantastic goalkeeper and a fantastic lad.
"If he does make a bad decision the ball ends up in the back of the goal - he knows that is part of the territory for him.
"He sets massively high standards for himself and when it doesn't go for him people are quick to jump on his back.
"He knows he has the full backing of the whole squad and I am sure he is delighted to be here and he is looking forward to playing."
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