Chesterfield manager Paul Cook admitted the club's season was in the balance until his substitutes sealed a 2-0 win that keeps them in the chase for the play-offs.
Ivorian striker Armand Gnanduillet and Jack Lester finally broke Wimbledon's resistance in the second half to leave the visitors at the bottom of npower League Two.
Cook said: "It was a game that if we hadn't had won, I'm not saying our season would have been over but it would have been a challenge to get into the play-ofs. Every point is vital and I told the lads at half-time, this is our season here in the second half and we will not get this back.
"We had to remain patient, strong and believe in what we were doing and to a man I felt we did that. I thought the lads gave a great response. We were dogged, we defended well when we had to and when we counter-attacked, we looked a threat and that was pleasing for me as a manager."
Chesterfield had suffered an early setback when striker Marc Richards had to go off in the 20th minute with a hamstring injury and despite dominating possession, the home side created little in a shapeless first half.
Both sides made changes and Gnanduillet struck in the 59th minute when he sidefooted Danny Whitaker's ball in from the left past Neil Sullivan.
The veteran goalkeeper kept his side in the match with a superb save in the 76th minute when he flew to his right to tip away a 20 yard drive from Drew Talbot but he was beaten again seven minutes from time.
Wimbledon were caught pushing forward and Gnanduillet broke away to put Lester in on the right and the striker beat Sullivan with a low shot across the keeper. And Wimbledon manager Neal Ardley could not hide his anger after a second away defeat in five days leaves them fighting for their Football League status.
"I felt at half time we were an accident waiting to happen," he said. "We made substitutions to get a little bit more of a stranglehold on the game but one of them has cost us the game. People are not winning their individual battles, they're two yards off the pace and they're not sticking to the game plan we set out.
"There's not enough passion, not enough steel, not enough work rate, all the things we talked about. I am not taking anything from this. At the moment I am seething and I am hurting and I hope the players feel the same way."