The league winner is awarded a bye to the ZP Final, whilst the second-and-third-placed teams will need to contest a semi-final. The Saints lie third behind Bath and Wasps, and – with one round only remaining – are unable to catch either side.
Gloucester's victory on Saturday pulled them within three points of the Saints and can steal the third slot if they manage to beat Bath next week, and Northampton fail to beat NEC Harlequins.
But back to matters at Headingley!
Leeds actually got the scoring going when Alan Dickens skipped through early in the game after intercepting an inside pass and sprinting 65 metres to touch down.
But the visitors were fully aware of the looming 'Cherry and White' cloud at the shoulder, and struck back when Darren Fox burrowed over from close-range in the 28th minute.
The Saints looked to be in trouble when they lost England fly-half Paul Grayson to injury after the half-hour mark, and the Tykes went to the break with a 10-8 lead.
The Saints piled into the second half with steely determination, and good handling saw Nick Beal dash through a gap to score under the posts.
Grayson's deputy, Shane Drahm, slotted the conversion and a pair of penalties shortly afterwards to put Northampton 11 points clear.
Saints extended their lead when Ben Cohen palmed down a chip ahead to Andy Vilk, who fed a pass back to the England star who sauntered in for the score.
Leeds pushed forward and a spell of sustained pressure was finally rewarded when former England wing David Rees touched down.
But it was the Saints who had the last word, as Drahm's pin-point kick was gathered by Cohen who duly put the result beyond doubt by sealing his brace of tries.
For Leeds Tykes:Tries: Dickens, ReesCon: RossPen: Ross
For Northampton Saints:Tries: Fox, Beal, Cohen 2Con: DrahmPens: Grayson, Drahm 2