The visitors looked to have secured victory until Sam Togwell rescued a point for the Spireites by driving home a low shot after a corner was touched on.
It leaves Chesterfield, ninth in the League Two table, four points adrift of seventh-placed Bradford with three matches remaining
Crossley said: "I thought it was a fantastic game, right to the death from the first whistle. It was like an FA Cup tie really and I think in the end it was fair result.
"Both managers said at the end what a great game it was and I think both teams have to be happy with a point.
"We talk about defining moments in football and maybe that goal in the last couple of minutes was our defining moment of the season, who knows? We are still in there and realistically there are three teams who can get that final spot and we are one of them.
"All you can do is stay in it as long as possible and we are doing that. There are three games to go and if we win all three, I believe we will get that final spot."