Northampton's starting team shows three personnel changes after earning a dramatic late bonus point at Saracens last weekend.
Kahn Fotuali'i comes in at scrum-half with the other two changes coming in the pack, with Phil Dowson and Sam Dickinson both starting alongside Tom Wood in the back row.
Meanwhile Calum Clark, who was named as the Player of the Month for March earlier this week, could make his one 100th first team appearance in just his fourth season at Franklin's Gardens after being named on the replacements' bench.
London Irish fly-half Shane Geraghty will captain the Exiles against his former club.
Geraghty captains the side in the absence of George Skivington who misses the match with a back injury.
Marland Yarde replaces Topsy Ojo on the wing; Ojo fractured his jaw in the victory over Newcastle last weekend. James O'Connor has a hamstring injury and is replaced at full-back by Alex Lewington.
Matt Parr, Mike Mayhew and Leo Halavatau start in the front row for a second week with Kieran Low replacing Skivington in the second row to join Nic Rouse.
Gerard Ellis, who scored on his Aviva Premiership debut last week, will start in the back row with Blair Cowan and Ofisa Treviranus.
TomÃ¡s O'Leary and Geraghty will start at half back with Eamonn Sheridan and Fergus Mulchrone in the centre. Andrew Fenby, Yarde and Lewington make up the back three.
"We enjoyed a good win last weekend but have picked up a few injuries for our troubles," said Irish boss Brian Smith.
"The players stepping in know they have big shoes to fill. Northampton will be a step up this weekend; Franklins Gardens is always a tough place to go so we know we will have to be at our best to compete."
Form: Franklin's Gardens had been a fortress up until Round 18, as Leicester Tigers ended a nine-game winning streak on home turf. At least one piece of history remains on the Saints' side however, with the Exiles having secured just one victory in Northampton since 2004 - edging past 14-13 in September 2011. But buoyed after inflicting a 40-12 defeat against Newcastle Falcons last weekend, Irish will present an almighty challenge - and Waller insists his side must not be caught cold again. The Exiles have won just once at Franklin's Gardens in ten years.
For Northampton Saints: 15 Ben Foden, 14 Jamie Elliott, 13 George Pisi, 12 Luther Burrell, 11 George North, 10 Stephen Myler, 9 Kahn Fotuali'i, 8 Sam Dickinson, 7 Tom Wood (c), 6 Phil Dowson, 5 Courtney Lawes, 4 Samu Manoa, 3 Salesi Ma'afu, 2 Ross McMillan, 1 Alex Waller
Replacements: 16 Matt Williams, 17 Ethan Waller, 18 Gareth Denman, 19 Calum Clark, 20 GJ Van Velze, 21 Lee Dickson, 22 Will Hooley, 23 James Wilson
For London Irish:: 15 Alex Lewington, 14 Marland Yarde, 13 Fergus Mulchrone, 12 Eamonn Sheridan, 11 Andrew Fenby, 10 Shane Geraghty (c), 9 TomÃ¡s O'Leary, 8 Ofisa Treviranus, 7 Gerard Ellis, 6 Blair Cowan, 5 Nic Rouse, 4 Kieran Low, 3 Leo Halavatau, 2 Mike Mayhew, 1 Matt Parr
Replacements: 16 Jimmy Stevens, 17 Johnny Harris, 18 Jamie Hagan, 19 Bryn Evans, 20 Jebb Sinclair, 21 Tom Homer, 22 Ian Humphreys, 23 Darren Allinson
Date: Sunday, April 20
Venue: Franklin's Gardens
Kickoff: 14:00 (local, 13:00 GMT)
Referee: JP Doyle
Assistant Referees: Andrew Pearce, Nigel Carrick
TMO: Geoffrey Warren