For the Saints, Australian Peter Jorgensen comes in to take his place, in a side which sees Scotland prop Tom Smith absent after breaking his toe during an epileptic fit this week.
There has been better fitness news for a trio of their stars however, as fly-half Paul Grayson, flanker Grant Seely and second rower Matt Lord have all passed fitness tests – Grayson and Lord starting, while Seely sits in the bench.
For Quins, there are three changes to the side which lost to regular season champions Gloucester in their last outing.
Back rower Ace Tiatia is suspended, with Roy Winters taking his place on the blindside, with Scott Bemand coming in at scrum-half after Billy Fulton dislocated a bone in his wrist.
The final change in the starting XV is at tighthead prop, where Jon Dawson comes in for England veteran Jason Leonard, who is rested from the match.
Harlequins are currently seventh in the Premiership table, two places behind Northampton, with Quins Chief Executive Mark Evans saying ahead of the match: "This is an important game for us.
"A win against Northampton will guarantee us a place in the Wild Card play-offs and will give us a shot at qualifying for next season's Heineken Cup.
"However, Northampton are also looking to qualify for the Heineken Cup by finishing in fourth place in the league, so we know that we are going to face a tough battle."
Harlequins: 15 Nathan Williams, 14 Dan Luger, 13 Will Greenwood, 12 Mel Deane, 11 Ben Gollings, 10 Paul Burke, 9 Scott Bemand, 8 Tony Diprose, 7 André Vos (captain), 6 Roy Winters, 5 Simon Miall, 4 Bill Davison, 3 Jon Dawson, 2 Tani Fuga, 1 Ceri Jones.Replacements: 16 James Hayter, 17 Bruce Starr, 18 Karl Rudzki, 19 Luke Sherriff, 20 Laurent Gomez, 21 Matthew Powell, 22 Rob Jewell.
Northampton Saints: 15 Nick Beal, 14 Oriol Ripol, 13 Peter Jorgensen, 12 John Leslie, 11 Ben Cohen, 10 Paul Grayson, 9 Matt Dawson, 8 Andrew Blowers, 7 Budge Pountney (captain), 6 Darren Fox, 5 Mark Connors, 4 Matt Lord, 3 Robbie Morris, 2 Steve Thompson, 1 Brett Sturgess.Replacements: 16 Matt Miles, 17 Kelvin Todd, 18 Rob Hunter, 19 Grant Seely, 20 James Brooks, 21 Mark Tucker, 22 Jon Sleightholme.
Kick-off: 19.45 (18.45 GMT)
By Mark Smith