Chris Ashton marked his final game in a Northampton shirt at Franklin's Gardens with a try as the Saints overcame Worcester 42-14.
The Saints will travel to Harlequins in the Premiership semi-final after what turned out to be a comfortable win against a depleted Warriors outfit but they didn't have it all their own way, coming up against more resistance than expected at times.
Ashton opened the scoring inside five minutes with a try on his final appearance at Franklin's Gardens after England team-mate Ben Foden had cut the Worcester defence to ribbons down the left wing and provided the killer inside pass to the Saracens-bound winger.
Just as most were expecting the floodgates to open for the hosts though, Josh Drauniniu levelled the scores for the visitors, exchanging passes with full-back Tom Arscott in the midfield on his way to scoring underneath the posts.
Although the Saints spent large periods of the first half camped in the opposition twenty-two, it took them until just before half-time to hit the front with a hamstring injury to try-scorer Ashton midway through the half not helping their momentum either.
But they kept banging on the door and, after Shaun Perry was sin-binned and Stephen Myler had knocked over a simple penalty, Foden smashed through the tackles of Alex Grove and Danny Gray to score a crucial try and make it 17-7 at the break.
Myler was successful with another penalty at the start of the second half but again Worcester refused to play the role of disinterested opponents and hit back with a short-range try from Kai Horstmann after a good burst from replacement scrum-half Jonny Arr.
Ryan Lamb came on for Myler soon afterwards and slotted another three points to stretch the lead to nine points and then the replacement fly-half floated a superb wide pass to George Pisi, who put the ball on a plate for winger Paul Diggin to score in the corner.
With the win almost in the bag, replacement Teimana Harrison secured a bonus point with his first ever Premiership try after James Craig had stolen a Worcester lineout just metres from the try-line.
Alex Waller added a bit of extra gloss with a late pushover try as well to boost the Saints' confidence ahead of a tricky trip to Twickenham to face Harlequins in the semi-final.
Tries: Foden, Ashton, Diggin, Waller
Cons: Myler 2, Lamb 3
Pens: Myler 2, Lamb 2
Tries: Drauniniu, Horstmann
Yellow cards: Perry, Shervington (both Worcester)
Northampton: 15 Ben Foden, 14 Chris Ashton, 13 George Pisi, 12 James Downey, 11 Paul Diggin, 10 Stephen Myler, 9 Lee Dickson (capt), 8 Roger Wilson, 7 Phil Dowson, 6 James Craig, 5 Christian Day, 4 Mark Sorenson, 3 Brian Mujati, 2 Andy Long, 1 Soane Tonga'Uiha.
Replacements: 16 Ross McMillan, 17 Alex Waller, 18 Paul Doran Jones, 19 Ben Nutley, 20 Teimana Harrison, 21 Martin Roberts, 22 Ryan Lamb, 23 Tom May.
Worcester: 15 Tom Arscott, 14 Miles Benjamin, 13 Alex Grove, 12 Ravai Fatiaki, 11 Josh Drauniniu, 10 Danny Gray, 9 Shaun Perry (c), 8 Kai Horstmann, 7 Matt Kvesic, 6 Neil Best, 5 Craig Gillies, 4 James Percival, 3 Bruce Douglas, 2 Chris Fortey, 1 George Porter.
Replacements: 16 Ed Shervington, 17 Ryan Furniss, 18 Ceri Jones, 19 Ben Gulliver, 20 Sam Betty, 21 Jonny Arr, 22 Joe Carlisle, 23 Charlie Hayter.
Referee: Greg Garner