The Scotland openside failed a fitness test on a neck injury on Friday, with youngster Darren Fox taking his place, Wallaby Mark Connors moving from lock to blindside and Wales' Steve Williams coming into the starting XV in the second row.
Saints coach Wayne Smith said ahead of the key match: "Tomorrow’s [Saturday's] game is a great opportunity for us, but we have a very big obstacle in the way – Leeds.
"You have to admire the way in which Phil Davies and his team have learned the lessons at this level, and how they have applied them.
"To achieve the results they have this year shows not just character and spirit, but brains as well."
The match, should Saints not progress to the play-offs, will mark the last in the Saints colours for centre Peter Jorgensen, prop Matt Stewart and scrum-half Ian Vass, as well as Simon Hepher and Kelvin Todd.
Northampton Saints: 15 Nick Beal, 14 Bruce Reihana, 13 Peter Jorgensen, 12 John Leslie (captain), 11 Ben Cohen, 10 Paul Grayson, 9 Matt Dawson, 8 Andrew Blowers, 7 Darren Fox, 6 Mark Connors, 5 Matt Lord, 4 Steve Williams, 3 Robbie Morris, 2 Steve Thompson, 1 Matt Stewart.Replacements: 16 Matt Miles, 17 Chris Budgen, 18 Rob Hunter, 19 Grant Seely, 20 James Brooks, 21 Mark Tucker, 22 Oriol Ripol.
Kick-off: 15.00 (14.00 GMT)
By Mark Smith
