The 37-year-old marked his 395th and last League game with a penalty and a typically clinical finish after Jay O'Shea and Marc Richards had opened the scoring.
Chesterfield assistant manager Tommy Wright said: "I think the players wanted to win it for Jack. It was great for him to score two goals and I don't think the script could have been better with him getting our first penalty in the league this season and dinking it like Panenka the Czechoslovakian.
"It was a great day and it's a credit to all the players that they put on a performance like that for a great professional and a good man. He's been a model professional, he's always wanted to play every game. He's been a great finisher and I'm sad to see him go."
Chesterfield had been tipped as one of the favourites for promotion and Wright admitted: "In the last six or seven weeks the form has been quite good but the league doesn't lie.We have good players at the club and everyone should be optimistic for the coming season."