Ben Nutley scored twice to help the Wanderers beat Worcester Cavliers 16-13 and secure a home play-off semi-final in the Aviva A League.
It was a fine comeback from the Saints second string, who had been 13-3 down at half-time thanks to a Matt Gilbert score and eight points from the boot of ex-Northampton fly-half Ryan Lamb.
The Wanderers went into the game on the back of a 34-10 victory at Sale Jets a week earlier.
They knew a win would secure top spot in the Northern Conference and a strong side was named, with JJ Hanrahan, Jamie Elliott and James Wilson among the men taking to the field.
But it was to be Worcester who started the stronger at Franklin’s Gardens, with Gilbert giving the away side the lead after effective lineout work.
Lamb added the extras before Hanrahan saw his ambitious penalty attempt fall short of the posts.
The Wanderers were hit with another blow when full-back Wilson was forced off after feeling the effects of a tackle early on.
And Lamb soon put Worcester 10-0 up, landing a penalty earned at the scrum.
Hanrahan got the home side on the board on 28 minutes, kicking a penalty he helped to win.
But Lamb cancelled that out on the stroke of half-time with another successful effort from the tee.
The Wanderers knew they needed to up their game to keep their qualification hopes alive, and that was what they did, forcing Dan Sanderson to infringe.
Sanderson was sent to the sin bin and Worcester were punished immediately as a big maul carried Nutley, who had scored twice in the win at Sale, over for the score.
Worcester were down to 13 six minutes later, when Dean Hammond took Elliott out in the air.
Hanrahan closed the gap further with a penalty on 65 minutes and with the momentum firmly with them, the Wanderers pushed for the win.
And after Lamb was yellow carded, Nutley popped up again from a tried and tested lineout move, making it four tries in two games for the flanker and sealing the semi-final spot.
The Wanderers will now host Saracens or Exeter, who complete their A League schedule next Monday.
The semi-final date is initially scheduled for April 25, but remains to be confirmed.
Wanderers: Wilson (Furbank 16); Elliott, Hutchinson, Olver, Collins; Hanrahan (Packman 65), Kessell; E Waller, Fish, Denman (Parkins 49); Onojaife, Moon (Peters 63); Paterson, Ludlum, Nutley.