Chesterfield took the lead twice but were pegged back on both occasions by Leyton Orient’s David Mooney before Dean Cox took full advantage of an injury time mistake by Tommy Lee.
An Elliot Omozusi own goal had restored the Spireites’ lead ten minutes in to the second half, after Mooney had cancelled out Jay O’Shea’s penalty kick during a flat first 45 minutes.
Lee had made several crucial stops during the match but an uncharacteristic error in the 11th minute of time added on handed the League One strugglers three valuable points.
The result meant Chesterfield remain outside of the play-off picture ahead of Tuesday night’s trip to Scunthorpe United while the visitors Orient jump off the bottom of the table.
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