The midfielder, who was recently offered a new deal by the League Two outfit, is attracting interest from as high up as the Championship, with Derby reported to have made an enquiry.
But the Cobblers are holding out for what they consider to be a fair price for the 20-year-old, who is out of contract but protected by the Bosman ruling.
"Michael is a very valuable player to us and if anything should happen it has got to be for the right price," Cardoza told the Northampton Chronicle & Echo. "The season has only just finished. People will have made their offers to their players and they will be waiting to hear back over the next couple of weeks so they won't be able to get their squads properly together until they know who is staying and who is going.
"It's always going to be a little bit quiet at this time but things will probably hot up at the end of this month and towards the start of the next.
"You don't want these issues to drag on because it does affect things, but it will take as long as it takes. There's no rush. We have made him an offer and that's where we are with it."