Northampton fell to a fourth consecutive defeat after a poor performance against Hereford.
Nathan Elder fired the visitors in front after Harry Pell's shot was saved by Cobblers keeper Sam Walker.
Steven Leslie's deflected free-kick doubled the Bulls' advantage before Saido Berahino pulled one back for the hosts from close range.
Pell secured the victory with a diving header after he exchanged passes with Tom Barkhuizen.
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Cobblers boss Gary Johnson told BBC Radio Northampton:
"They know they didn't perform individually or as a team today.
"I still felt there were a lot of opportunities that we could have tucked in - especially in the second half.
"But football is football - you have to keep going and work hard to turn it around."
Hereford manager Jamie Pitman told BBC Hereford and Worcester:
"Our pure energy and fitness are getting us wins at the moment. In two or three months that will be even higher.
"They had a spell in the second half when they put us under a lot of pressure but we generally soaked it up and coped well.
"We looked very good on the counter attack and our wide men allow us to do that.
"After their first goal it could have gone either way so obviously the important goal was our last goal."