The centre-half moved to Peterborough late on Friday evening for £500,000. But Cooper revealed Pools were willing to reject the bid and make Baldwin a new contract offer.
But Baldwin wanted to go ahead with the offer and make a return to League One, a change of heart on Friday afternoon giving enough time for the transfer to be completed.
“Things have to fall into place and the thing I didn’t expect was Jack to be attracted. Lunchtime on Friday he wasn’t – by two o’clock he was. I suggest that’s his representatives and not Jack,’’ revealed Cooper.
“He’s due to become a father in eight weeks, he sees the financial side of it. We were ready to extend his contract and offer a new deal.
“Peterborough have actually showed their hand, so he was our most valuable asset.
“We wanted to keep him here as long as he could. His ear had been turned and told us he would like to pursue the offer.
“As a football club, what do you do? We were under no pressure to sell anyone.
“He said he felt it was right for him as a player, and it was right for him financially and geographically.
“We are disappointed, but Peterborough have done it the right way. We have been compensated for his exit and see where it leaves us.’’ Cooper will now seek to boost his squad when the emergency loan transfer window opens next week.
And he added: “There was no scope for change immediately, but we were going to be without Jack for a fortnight through suspension anyway.
“His move won’t adjust what happens to us. We give Sam his due and a pat on the back for the way he has approached everything in recent months.
“But we would be very naïve if we hadn’t started to look what is out there and who could be available on loan.
“We are not in the market to accumulate players, they have to come straight in. We are looking and the Newport game on the 15th of February would have been the time when we had Jack available anyway.
“So let’s see if anything is in place. But we can ill afford to lose anyone through suspension or injury.
“When I spoke to Jack on Friday morning he was happy. I said there was better out there and if he was willing to give it six months, 18 months, and he could go straight into the Championship.
“That period of development in a young centre-half would mean an awful lot. He has had his head turned in a few hours.
“And that was only by his representatives. He was happy with us and we wanted to negotiate a new contract.
“From leaving us until the deal was done there was a lot of things going on with his representatives.’’