Worrall's second-half strike the difference as Cobblers slip to first league defeat of 2020
Cobblers suffered their first home defeat in more than four months when beaten by David Worrall's second-half header as promotion rivals Port Vale edged them out at the PTS Academy Stadium on Saturday.
Leyton Orient were the last visiting team to win at Sixfields way back on October 5 but Vale repeated that feat when scoring the game's only goal through Worral 17 minutes from time.
A dour first-half came and went without incident before Cobblers dominated much of the second but it was a rare wasteful day in front of goal with visiting goalkeeper Scott Brown making three excellent saves.
The only ray of sunshine for Northampton came in the shape of results elsewhere as only three of the other top eight in Sky Bet League Two picked up victories.
Cobblers drop a place to sixth and there's now extra signifcance on Tuesday's visit of league leaders Swindon Town
Keith Curle selected another bold starting line-up as the three January signings who were ineligible for Tuesday's FA Cup tie all returned to face Port Vale.
Lloyd Jones got the nod in defence despite Jordan Turnbull returning to the matchday squad, Mark Marshall was at wing-back and Callum Morton started up front, with Sam Hoskins in central midfield.
Vale's David Worrall was wide of the mark with an early half chance but that was a rare moment of action in an otherwise disappointing start to the game.
Marshall had Town's first sight of goal when heading Scott Wharton's cross straight at the visiting goalkeeper but the breezy conditions were a hindrance for both sides and that was reflected in a low-quality opening 45 minutes.
Cobblers marginally improved as the first-half wore on and they threatened on a few occasions with Jones' close-range shot blocked and Hoskins unable to convert from the subsequent corner.
Nicky Adams forced Scott Brown into a decent stop with a long-range shot and Morton close to snaffling up the rebound before Richard Bennett headed over with the last act of the half.
Morton shot into the side-netting just moments into the second-half and Adams then missed the game's best chance up until that point, side-footing wide when left unmarked 12 yards out.
Cobblers were turning up the heat and Hoskins' superbly struck volley was matched by Brown's flying save before he sent another effort over the crossbar.
David Cornell made his first save just past the hour-mark when showing good hands from James Gibbons' fierce strike but Brown continued to be the busier 'keeper and he produced a smart stop to thwart Vadaine Oliver's powerful volley.
However, Vale moved into a surprise lead with 17 minutes to go when Tom Conlan got away down their left side and whipped in a deep cross that left Worrall with a simple headed finish.
Brown continued to frustrate the Cobblers as he denied Adams' stinging volley with 12 minutes to go and despite having plenty of corners and attacking throw-ins late on, the Cobblers couldn't break down a stubborn Vale defence.
Cobblers: Cornell, Jones, Goode, Wharton, Watson (lines 85), Anderson (Warburton 72), Marshall, Adams, Hoskins, Morton (Williams 60), Oliver
Subs not used: Arnold, Turnbull, Martin, Harriman
Port Vale: Brown, Gibbons, Joyce, Brisley, Legge (c), Worrall, Conlan, Burgess (Smith 85), Bennett (Pope 58), Clark
Subs not used: Oyeleke, Atkinson, Cullen, Browne, Maddison
Referee: Charles Breakspear
Vale fans: 461