Chris Wilder was named Manager of the Month in the build-up to the game and saw his side take an immediate lead, Joel Byrom netting in the first minute.
Devitt levelled for the Shrimps before half-time but Marc Richards was again the decisive figure as he netted the 54th minute winner that takes Northampton above their visitors and firmly into the top-half of the League Two table.
More to come on Cobblers Mad