Dean Saunders says the £1.3m transfer of Sam Clucas will allow him to add quality players to his Chesterfield squad.
Clucas, who joined Spireites at the start of the 2014/15 season from rivals Mansfield Town, will have a medical at Hull City on Monday ahead of an expected move to the promotion-chasing Championship side.
Mansfield Town will get a cut of the fee as part of a sell-on clause included in the previous £100,000 transfer.
And, although disappointed, Saunders said the deal represented good business for Chesterfield.
“For a club like ours we cannot turn this down, we have to remember where we are.
“I am very disappointed to have lost him, but he is going to a big club who were in the Premier League last year.
“We have got a big transfer fee for a League One player, there are not many League One clubs who get a transfer fee like that.
“He is probably one of our better players and, as the manager, I am disappointed to have lost him, but good luck to him.
“We can’t stand in the way of anybody. I expected this sort of thing could happen but having paid £100,000 a year ago, it’s very good business for a League One club.
“I will have some money to reinvest into the squad. I’ve been shopping in Lidl up to now, but now I’m going to be shopping at Marks & Spencer.
“No doubt we will sign two or three good players, who can make a difference to us. They are going to have to be decent players to get into our tem.
“I was prepared for something like this and I have still got my guard up. The players did well last season and there are still vultures out there.
“I can now sign a different type of player. I can assure the supporters that the players we bring in will be good
Clucas scored nine goals during 38 appearances for the League One side last season and played a key role in Chesterfield’s march to the play-offs.
It is the latest high-profile departure from the Proact Stadium after Gary Roberts was sold for an undisclosed fee to Portsmouth.