League Two leaders Chesterfield surrendered a three-goal half-time lead to lose 4-3 at Morecambe on Saturday.
An Eoin Doyle brace and Gary McSheffrey's first goal since December 2012 fired the Spireites 3-0 ahead inside the opening 23 minutes at the Globe Arena.
However, the hosts stormed back after the break, as goals from Kevin Ellison, Mark Hughes, Jack Sampson and Padraig Amond turned the game on its head to give Jim Bentley's men their first win in three matches.
Oxford United failed to capitalise on Chesterfield's loss. The U's, who were beaten 2-0 at Rochdale, drop down to fourth in the league table.
Fleetwood Town and Exeter City move above Oxford into the automatic promotion places.
The Shrimpers won 3-1 at Bristol Rovers, while Exeter beat Devon rivals Plymouth Argyle by the same scoreline at St James Park in the day's early kickoff.
The biggest shock of the day came at Field Mill, where high-flyers Mansfield Town were thrashed 4-1 by Hartlepool United.
Jack Compton netted twice for Pools, who climb to 19th after recording their first away win of the season.
Elsewhere, Portsmouth and Scunthorpe United registered comfortable home victories over Rochdale and Cheltenham Town respectively.
Meanwhile, there were away wins for Northampton Town, York City and Burton Albion. The match at Gigg Lane between Bury and Newport County ended goalless.
Results in full: AFC Wimbledon 0-2 Northampton, Bristol Rovers 1-3 Fleetwood Town, Bury 0-0 Newport County, Exeter 3-1 Plymouth, Mansfield 1-4 Hartlepool, Morecambe 4-3 Chesterfield, Oxford Utd 0-2 Southend, Portsmouth 3-0 Rochdale, Scunthorpe 2-0 Cheltenham, Torquay Utd 0-3 York City, Wycombe 1-2 Burton Albion.
