Regular skipper Johann Muller is sidelined with a displaced fracture in his arm, so 20-year-old Iain Henderson, who made his Ireland debut in November, has moved into the second row to partner fellow international Dan Tuohy.
New Zealander Nick Williams has been promoted from the replacements bench to fill the vacant loose forward spot, slotting in alongside stand-in captain Chris Henry and former Saint Roger Wilson.
Andrew Trimble will make his 50th Heineken Cup appearance in Saturday's encounter, following in the footsteps of Paddy Wallace and Tommy Bowe, who did so in rounds 2 and 3 of the competition respectively.
There is only one change among the replacements as Neil McComb steps in to replace the promoted Williams. Ricky Lutton will make his Heineken Cup debut if he takes to the pitch at any time during Friday's game.
The 26-year-old development prop has made one previous appearance - as a replacement in the RaboDirect PRO12 win over Edinburgh last month.
A victory for Ulster over Northampton would be another massive step towards progression to the knockout stages for the third consecutive season.
However, after much criticism regarding the manner of their defeat in the previous round, Northampton will be arriving at Ravenhill determined to gain revenge.
ULSTER (v Northampton Saints): Jared Payne; Tommy Bowe, Darren Cave, Paddy Wallace, Andrew Trimble; Paddy Jackson, Ruan Pienaar; Tom Court, Rory Best, John Afoa, Iain Henderson, Dan Tuohy, Nick Williams, Chris Henry (capt), Roger Wilson.
Replacements: Nigel Brady, Callum Black, Ricky Lutton, Neil McComb, Robbie Diack, Paul Marshall, Luke Marshall, Craig Gilroy.