Hooker and team captain Rory Best has been ruled out of contention, having not fully recovered from the rib injury he sustained in the closing stages against Biarritz.
His place has been taken by Nigel Brady, who was a starter for the back-to-backs over Bath before Christmas. South African lock Johann Muller will captain the side.
Prop BJ Botha, who damaged ligaments in his elbow last time out, is also unavailable for this 'must win' game. The fit-again Declan Fitzpatrick comes in for Botha, for what will be his first start in this season's Heineken Cup.
Ulster are fighting it out with Biarritz for the top spot in Pool 4 and while Aironi are bottom of the pile with no possibility of qualifying, Brian McLaughlin knows the Italians will not make it easy for his side.
"You only have to look at Aironi. They're a very proud lot and certainly at home, they'll be a very difficult nut to crack," said the Ulster boss.
"They've already beaten Biarritz there in this competition, and we had a tough game against them when we went out there (in the league) in September so we're under no illusions.
"We know it's going to be an exceptionally difficult task, but if we want to get where we want to be well then we've got to go there and win. It's as simple as that - that's our focus for this week."
Other results last weekend mean that Ulster now only need a win, by any margin, to qualify for the quarter-finals.
The stakes are certainly high, but McLaughlin is wont to change the approach which served the province so well in round 5.
"The Glasgow result last week was certainly a plus for us, but we've got to focus in on the job we've got to do. We can't worry about what's happening elsewhere," he added.
"We have to be very, very much focusing and emphasising us - we have to get a win first and foremost. If we can put the icing on the cake with a bonus point, we'll worry about that later in the game."
ULSTER (v Aironi Rugby): Adam D'Arcy; Andrew Trimble, Nevin Spence, Paddy Wallace, Simon Danielli; Ian Humphreys, Ruan Pienaar; Tom Court, Nigel Brady, Declan Fitzpatrick, Johann Muller (capt), Dan Tuohy, Stephen Ferris, Willie Faloon, Pedrie Wannenburg.
Replacements: Andi Kyriacou, Bryan Young, Jerry Cronin, Tim Barker, Chris Henry, Paul Marshall, Ian Whitten, David McIlwaine.