Sam Hoskins grabbed the only goal of the game as 10-man Northampton held on to beat Oxford 1-0.
Cobblers goalkeeper Adam Smith had to be alert to thwart Callum O'Dowda after he raced into the box, but both sides struggled to create opportunities in a scrappy opening period.
That was until Cobblers broke the deadlock in the 23rd minute when Jason Taylor found Nicky Adams out wide and his pinpoint cross was headed home by Hoskins.
Danny Hylton flashed a shot across goal as Oxford tried to get back into the game and they should have been back on level terms before the break.
Taylor was sent off on the stroke of half-time for an off-the-ball incident with O'Dowda in the box but Hylton's penalty was comfortably saved by Smith.
From the ensuing corner, Chey Dunkley headed over but Oxford had squandered a great opportunity to go in on level terms.
Ryan Taylor had an early chance after the restart when he raced clear but again Smith was quickly out to clear the danger.
Despite having the man advantage, Oxford failed to seriously trouble Northampton's rearguard before Smith tipped Dunkley's header over from O'Dowda's free-kick.
Smith enjoyed a comfortable second half as the Cobblers' well-drilled defence frustrated a disappointing Oxford side.
Marc Richards had a late header saved by Sam Slocombe but Hoskins' goal proved enough.
Source : PA