Regular captain Johann Muller suffered a calf injury in the team run on Wednesday and has been withdrawn as a precaution.
All Black prop John Afoa will take over as skipper for the night and he is joined in the front row by Andi Kyriacou and Callum Black, who makes his second start for the Ulstermen.
Muller's absence means Lewis Stevenson will partner Tuohy in the second row, while Mike McComish, Willie Faloon and Robbie Diack form an athletic back row trio.
The half-back pairing of Ruan Pienaar and Ian Humphreys remains in place, as does the centre partnership of Wallace and Ian Whitten.
Adam D'Arcy will start at full-back, with the versatile Stefan Terblanche moving to left wing and Craig Gilroy switching to the right side.
Paddy McAllister has returned from injury to be included among the replacements, providing front row cover along with Nigel Brady and Adam Macklin.
The experienced Tim Barker and Academy player Ali Birch are the other forward replacements. Paul Marshall, Nevin Spence and Danielli complete the matchday squad.
Ulster head coach Brian McLaughlin is confident that the absence of some experienced players will be offset by the hunger of the players coming in.
"We're delighted to have the guys away with Ireland, it's important that individual players get recognition for their performances with Ulster," he said.
"With those guys away, it gives others a chance to come in and push themselves. It's important for the squad that we give as many opportunities as possible to players as we have to be in a position where we have depth in each area."
Commenting on the late withdrawal of Muller, he explained: "Johann got a tight calf during the team run yesterday (Wednesday) and after a scan we had a slight fear that it would develop, so we decided not to risk him.
"But it gives Lewis Stevenson the chance to step in and get some more game-time, and Tim (Barker) will get some action from the bench."
The Dragons have lost their previous 10 games on the road but McLaughlin is taking nothing for granted despite having home advantage.
"It's good to be back at Ravenhill in front of our home crowd but form counts for very little when you're playing the Dragons. They are always difficult to beat and they will be as determined as ever to stop the rot."
There are still tickets available for Friday's game. They can be bought online by clicking here or calling the ticket office on 02890493222 (ticketing option). Alternatively, you can pay at the gate on the night.
ULSTER (v Newport Gwent Dragons): Adam D'Arcy; Craig Gilroy, Ian Whitten, Paddy Wallace, Stefan Terblanche; Ian Humphreys, Ruan Pienaar; Callum Black, Andi Kyriacou, John Afoa (capt), Lewis Stevenson, Dan Tuohy, Mike McComish, Willie Faloon, Robbie Diack.
Replacements: Nigel Brady, Paddy McAllister, Adam Macklin, Tim Barker, Ali Birch, Paul Marshall, Nevin Spence, Simon Danielli.