Ulster have included Ireland international Stephen Ferris on their bench for Friday's hosting of Magners League surprise package Treviso.
In the back-line, only Simon Danielli retains the same position he played in the New Year's Day derby against Munster in Limerick, while Paddy Wallace moves from fly-half to inside centre.
Elsewhere it's all change as D'Arcy replaces Smith at full-back with Andrew Trimble featuring on the wing, Nevin Spence is recalled to partner Wallace in the centre and Humphreys and Pienaar form the half-back partnership.
Up front Tom Court, another player rested last week as part of the player management programme, and BJ Botha start with captain Rory Best.
Johann Muller returns to action partnered by Tim Barker who retains his place from last week while Chris Henry and Pedrie Wannenburg start ahead of TJ Anderson and Robbie Diack in the back-row.
Meanwhile, Treviso head into the fixture on the back of back-to-back victories over countrymen Aironi and make wholesale changes for the trip to Belfast.
Lorenzo Cittadini, Gonzalo Padr˛ and Marco Filippucci come into the pack for Pedro Di Santo, Antonio Pavanello and Paul Derbyshire while Fabio Semenzato is at number nine for Tobias Botes, who warms the pine.
In the back-line, Gonzalo Garcia drops to the bench so Andrew Vilk is on the wing, with Tommaso Benvenuti going into centre alongside Alberto Sgarbi.
Form: Ulster have won all five previous encounters with Treviso in all competitions. Ulster have lost their last two matches to Leinster and Munster and have not won at Ravenhill in the Magners League since Glasgow were the visitors on 1 October. Benetton Treviso took both "legs" of the Italian derby with Aironi over the holiday season. Treviso have not won a game outside of Italy since a trip to the Dragons in the European Cup on 15 December 2007.
Ulster: 15 Adam D'Arcy, 14 Andrew Trimble, 13 Nevin Spence, 12 Paddy Wallace, 11 Simon Danielli, 10 Ian Humphreys, 9 Ruan Pienaar, 8 Pedrie Wannenburg, 7 Willie Faloon, 6 Chris Henry, 5 Tim Barker, 4 Johann Muller, 3 BJ Botha, 2 Rory Best (capt), 1 Tom Court.
Replacements: 16 Nigel Brady, 17 Bryan Young, 18 Declan Fitzpatrick, 19 Dan Tuohy, 20 Stephen Ferris, 21 Paul Marshall, 22 Ian Whitten, 23 David McIlwaine.
Treviso: 15 Kristopher Burton, 14 Ludovico Nitoglia, 13 Tommaso Benvenuti, 12 Alberto Sgarbi, 11 Andrew Vilk, 10 Willem De Waal, 9 Fabio Semenzato, 8 Manoa Vosawai, 7 Alessandro Zanni, 6 Marco Filippucci, 5 Corniel Van Zyl, 4 Gonzalo Padr˛, 3 Lorenzo Cittadini, 2 Leonardo Ghiraldini, 1 Ignacio Fernandez Rouyet.
Replacements: 16 Franco Sbaraglini, 17 Augusto Allori, 18 Pedro Di Santo, 19 Valerio Bernab˛, 20 Paul Derbyshire, 21 Francesco Minto, 22 Tobias Botes, 23 Gonzalo Garcia.
Date: Friday, January 7
Referee: Leighton Hodges (WRU)
Assistant Referees: J Carvill, D Connolly (both IRFU)
TMO: Marshall Kilgore (IRFU)