The 22-year-old, currently on-loan with Ipswich, has made just one league appearance for his parent club since Pardew took over at the start of 2015.
“Jonny and I just can't seem to come together. In pre-season he's fit and then gets injured again. It was a terrible tackle at Farnborough," Pardew told the Croydon Advertiser.
“We were at deadline day last month and I'm looking at my numbers and thinking I can't see Jonny getting a game.
“Really and truly, with the amount of time he's got, I can't keep him here and have him as a substitute.
“I know our fans love him, and again, he may have influenced the game at certain points as a sub more than others or he might have got himself up to speed. He might have."