Hughes had his contract offer formally withdrawn this week after stalling on a deal that would have put him on less money than he was on last season at Sixfields.
It means the sweeper will now spend the first day of pre-season training among the v
ast ranks of unemployed footballers, although Gray is confident he will get taken on somewhere.
The manager insists the pair have parted on good terms, but feels Hughes should have heeded his advice rather than that of his agent.
"Mark was on a very good contract because we had to lure him away from a Premier League club, and with us getting relegated we can't afford to keep him on those wages," said Gray.
"The budget had to be cut and we had to reduce our offer to him. The disappointing thing is it's all agent-driven.
"Whether Mark is being told by his agent that the grass is going to be greener somewhere else, I don't know.
"You wish sometimes players would listen to you a bit more and learn from your experience rather than take the advice of their agents.
"I think he will get fixed up, but he might find that he gets fixed up somewhere on less money than he was offered here.
"There are a lot of players out there at this time who can't get contracts, and there will be players who were offered deals at Christmas who wanted to wait and see, who now won't get clubs."
Gray's men returned to pre-season training for a double session today in heatwave conditions.
The weather is not the only thing that has been hot at Sixfields, with
the manager's phone ringing off the hook as agents try to get their players deals.
"I'm getting 20 phone calls a day from agents offering me umpteen
players because they've realised pre-season is starting and their clients haven't got clubs," he said.
"I've no idea if Mark has got any concrete offers but we were happy to give him the benefit of the doubt and extend our deadline.
"I didn't want to lose him but I'm sure something will happen for him, maybe up north or something.
"We had a conversation at the end of last season and we've parted on good terms.
"Personally I wish Mark all the best for the future."
