Keith Curle endured a losing return to Sixfields as his Oldham side were beaten 2-1 by Northampton.
Jon Guthrie and Kion Etete scored the decisive goals before half-time as the Cobblers made it four home wins in a row.
Guthrie gave Northampton the lead after 14 minutes, stabbing home from close range after Oldham made a mess of trying to clear Mitch Pinnock’s free-kick.
Ali Koiki was close to adding an immediate second when his low cross-shot flashed wide and it was not long until Northampton did double their lead as a terrific team move ended with Etete volleying in Pinnock’s deep cross.
Sam Hoskins dragged a good chance wide late in the half and Oldham were back in the game nine minutes into the second half through Carl Piergianni’s scrappy finish at the back post.
The visitors were much better in the second half but they could not force an equaliser with Hallam Hope glancing a header wide and Jamie Hopcutt blazing over late on.