Wales juggernaut George North put his countrymen to the sword once more as Saints claimed a crucial 20-9 Champions Cup win at Ospreys.
North had scored four tries in the 34-6 victory over the PRO12 leaders at Franklin’s Gardens in October and he was on the mark again at the Liberty Stadium.
It was a timely score for Saints, who were down to 14 men at the time following George Pisi’s yellow card for a tip tackle on Dan Biggar.
And Ospreys, who only had three Biggar penalties to show for their efforts, barely rallied after the break as Stephen Myler’s boot put the game beyond them.
Calum Clark’s effort had got Jim Mallinder’s men up and running on a cold night in Wales and North’s opportunism, allied with Myler’s kicking, got the job done.
It means Saints are now level on 19 points with Racing Metro, who they play in a winner-takes-all showdown at Franklin’s Gardens on Saturday.
But Northampton may already have done enough to progress to the quarter-finals as their points tally is superior to most other sides in the competition.
They headed to Swansea backed by a small but vocal set of travelling fans, knowing that a win could prove so key in the bid to make the last eight.
The men in lime started brightly, but after a foray into opposition territory proved fruitless, Ospreys landed the first blow.
Biggar was on the money from the tee after Saints scramble’ defence had conceded a penalty and the home side were looking threatening.
Saints were disrupted by a knee injury to Ben Foden, who limped off to be replaced by James Wilson, but they adjusted quickly and were soon in front.
Tom Wood charged down Rhys Webb’s attempted clearance kick and Clark pounced on the loose ball to score.
Myler added the extras, but Biggar quickly cut the gap to a single point with another accurate penalty.
Saints were playing some flowing rugby when given the chance and good hands from Christian Day and the impressive Sam Dickinson pushed Ospreys into conceding a penalty.
Myler made no mistake with the kick, but Saints’ own discipline came into sharp focus soon after when Samoan centre Pisi was sin-binned for a tip tackle on Biggar.
Boos rang out, with the home fans were baying for a red card as their fly-half stepped up to notch the resulting penalty.
But Saints, who have become adept at playing with 14 men, were to strike back before the break as Justin Tipuric spilled the ball into North’s path and the Wales wing raced home.
Myler’s conversion handed Mallinder’s men an eight-point half-time lead and they had a solid scrum platform to build on at the start of the second period.
Ospreys were continually falling foul of Jerome Garces’ whistle and opted to change their props in a bid to stem the tide.
But they were also under huge pressure from the Saints’ driving game and Alex Waller was just short of the line as his side pushed for the line.
Ospreys were hanging by a thread and their supporters were growing increasingly agitated with the decision making of Garces, with cries of ‘cheat’ ringing out.
But Saints were struggling to get the crucial third try with passes going astray and the opposition proving a tough nut to crack.
Myler decided it was time to take some points, landing a penalty at the second attempt and the game was petering out with neither side showing the necessary thrust.
Ospreys did mount a late charge, desperately trying to give their fans something to shout about, but Saints stood tall to record an impressive away win.
Ospreys: Evans; Natoga (Dirksen 63), Beck, Matavesi, Walker; Biggar, Webb; M Thomas (G Thomas 50), Baldwin (Parry 63), Jarvis (Arhip 50); Bernardo (Lewis 63), Wyn-Jones (c); King, Tipuric, Ardron.
Replacements not used: Allen, Roberts, Davies.
Saints: Foden (Wilson 11); K Pisi, G Pisi, Burrell, North; Myler, Dickson; A Waller (Corbisiero 53), Hartley (c) (Haywood 70), Denman (E Waller 72); Dickinson, Day; Clark, Wood, Manoa (Dowson 70).
Replacements not used: Harrison, Hodgson, Elliott.
Referee: Jerome Garces