18 May, 11:09
IRFU Chief Executive Philip Browne has issued a statement following confirmation of Ronan O'Gara's decision to retire from playing professional rugby.
The only other alteration is on the bench where prop Bryan Young comes in for Declan Fitzpatrick, who has been sidelined by a wrist injury.
Craig Gilroy, Ulster's top try scorer in the Magners League with seven tries in nine appearances, could make his Heineken Cup debut if he comes off the bench during the game.
The Dungannon and Ireland Under-20 winger has been registered for the competition's knockout stages as an additional player.
Previewing the quarter-final clash with Northampton, flanker Henry said: "Everyone is going to have to bring their 'A' game to this one. They've threats throughout their team and definitely their back row is a very important factor for them.
"I think the breakdown is going to be pretty huge and as a unit we've talked about it and we really need to be on our game. They are a very confrontational side and very direct and we need to make sure we front up.
"Of course we would have preferred a home quarter-final, but we're not afraid to go anywhere at the moment. We've gone away from home and got wins so that gives us confidence.
"Also, knowing that we've beaten Bath two years in-a-row, both at home and away, is massive for us.
"I think, as well, you've got guys now brought into the squad with huge experience and that's definitely made a big difference.
"There's a great balance of guys. You've got Rory and Johann (Muller) saying the wise words to keep us all level-headed and then you've got that extra energy and enthusiasm from a guy who is just getting his first few caps."
Sunday's match will be shown live on Sky Sports 2, and there will also be commentary on BBC Radio Ulster 1341 MW from 2pm.
ULSTER (v Northampton Saints): Adam D'Arcy; Andrew Trimble, Nevin Spence, Paddy Wallace, Simon Danielli; Ian Humphreys, Ruan Pienaar; Tom Court, Rory Best (capt), BJ Botha, Johann Muller, Dan Tuohy, Robbie Diack, Chris Henry, Pedrie Wannenburg.
Replacements: Andi Kyriacou, Paddy McAllister, Bryan Young, Tim Barker, Willie Faloon, Paul Marshall, Ian Whitten, Craig Gilroy.