Players disliking eachother?

So basically I've just had 2 of my first team say they dislike their respective backup players. I really don't want to get rid of said backups as both have the potential to be world class. Any ideas how I can sort this out without having to sell anybody?

Edit: I've tried giving the first teamers new contracts, which sorted it our for a while. But about a month later I get the same message saying they dislike the player again.

Loan him out and get a replacement. Or give him a mentor of someone with a more professional personality and hope it rubs off onto him.