A sensational showing from Samu Manoa helped Saints beat Saracens 20-16 to ensure home advantage in the LV= Cup semi-finals.
Manoa played a part in all three of his team’s tries, scoring twice and helping to set up a first-half effort for Kiwi full-back James Wilson.
Academy fly-half Will Hooley also added five points with the boot to ensure Northampton will host Saracens in the final four on the second weekend of March.
Sarries had looked set to clinch the win when Ben Spencer, who grabbed a first-half try, took his personal tally to 16 points with a penalty 15 minutes from time.
But Manoa had other ideas as he dragged his team to victory by the scruff of the neck.
The American star had set the tone early on, welcoming Saracens flanker Matt Hankin to the game with a massive hit.
That gave the Saints pack the chance to turn on the power to win a penalty at the scrum and they used the possession well, winning a kick in front of the posts.
Debutant Hooley was unable to make it count, though, missing the chance to slot his first points for the Saints first team.
Northampton were eating their opponents for breakfast at the scrum, with the fledgling front row impressing for the second week in succession.
That laid the platform for the backs, who made the most of it as Kahn Fotuali’i, Jamie Elliott and Manoa combined superbly before the ball went wide to Wilson, who kinked inside to score.
Hooley eased his nerves by striking to conversion superbly to register his first points for the Saints first team before Spencer replied with a penalty for Saracens.
Saints were struggling on the discipline front and they were made to pay seven minutes before the break as Fotuali’i was sin-binned for a deliberate knock-on.
Saracens reaped immediate rewards as they pushed their hosts off the ball and Spencer dotted down.
The scrum-half gave the away side a 10-7 lead at the break and things remained that way as Fotuali’i returned three minutes after the interval.
The game needed a spark and Saints needed some inspiration.
They were to get it from Manoa, who finished off a flowing move down the left by bulldozing full-back Jack Ransom and diving over to score.
Hooley missed a tricky conversion from out wide but showed his character soon after, firing a penalty through the posts to extend his side’s advantage to five points.
Spencer soon replied, though, as the game remained finely poised heading into the final 20 minutes.
Saracens had their tails up with the introduction of experienced campaigners Jacques Burger and Mouritz Botha, and they took the lead through another Spencer penalty.
But Manoa wasn’t prepared to let the game slip and he surged over for another score in the corner with nine minutes to go.
Replacement fly-half Stephen Myler shanked the conversion and Fotuali’i made a similarly bad job of a drop goal attempt soon after.
But it mattered not as Saints saw out the game to ensure it is they who will have home advantage when the two teams meet again in the semi-finals on the second weekend of March.
Saints: Wilson; Elliott, G Pisi (Autagavaia 62), Waldouck, K Pisi; Hooley (Myler 63), Fotuali’i; E Waller (Warren 64), Haywood (McMillan 66), Denman (Parkins 55), Verbakel (Day 53), Manoa, Harrison (Williams 53), Nutley, van Velze (c).
Replacements not used: A Day.
Saracens: Ransom; Wilson, Streather (Stanley 40), Bosch, Tagicakibau; Mordt (c), Spencer; Gill (Barrington 27), Saunders (Spurling 53), du Plessis, Smith (Botha 53), Sheriff, de Jager (Burger 53), Hankin, Melck (Jubb 72).
Replacements not used: Lamositele, Maplesden.
Referee: JP Doyle