He was named ahead of Niall O'Connor yesterday, having replaced him in the last win against Munster.
Winger Mark McCrea will get his first competitive start for the Province.
The 21-year-old broke onto the senior scene last season as a rookie and soon was the talk of the town along with fellow Ulster Academy player at the time, Niall O'Connor.
Both went on to establish themselves as regular starters in the team and were soon offered fulltime professional contracts.
Ulster head coach, Matt Williams, said McCrea was "hungrier than ever" to get a start this season and fully deserved it after good performances against Portugal and Cardiff recently in friendly representative games.
McCrea comes into the side for Irish international, Andrew Trimble, who was ruled out on Wednesday evening after training with a minor injury.
Williams said: "Andrew pulled up during training. It is nothing serious, but we were not prepared to risk him.
Gaving Duffy will captain Connacht for the first time in a side which includes former Ulster and Irish scrumhalf, Kieran Campbell, on the bench.
ULSTER: B Cunnigham, T Nagusa, D Cave, P Wallace, M McCrea; I Humphreys, C Willis; J Fitzpatrick, R Best (capt), BJ Botha, D O'Donoghue, R Caldwell, S Ferris, D Pollock, R Diack.
CONNACHT: G Duffy (C); F Carr, M Deane, K Matthews, T Nathan; I Keatley, F Murphy; B Wilkinson, S Cronin, R Morris; M McCarthy, A Farley; R Ofisa, J O'Connor, C Rigney.
Replacements: A Flavin, R Loughney, A Browne, M Swift, K Campbell, T Donnelly, J Hearty.