In all, Ulster coach Mark McCall has made four changes to the team that started last week's Magners League defeat to Glasgow for the tussle with the Guinness Premiership leaders.
With a knee injury ruling back rower Stephen Ferris out for four to six weeks, Ulster will start with a new-look back row against Gloucester. Roger Wilson regains the number 8 jersey while Neil Best moves to openside with versatile lock Matt McCullough named as blindside flanker.
Kieron Dawson's leg injury, sustained in the Glasgow game, is not as serious as initially feared and he is named on the bench as back row cover.
In the battle of the second rows, Ryan Caldwell has been named on the bench with Italian World Cup lock Carlo Del Fava starting alongside former Wallaby Justin Harrison, while the front row of Justin Fitzpatrick, Rory Best and Bryan Young remains unchanged.
The one change in the back-line sees Wallace starting at out-half with Humphreys proving the back-up on the bench.
Speaking ahead of tonight's all-ticket game, coach McCall said: "This game has always been the most important fixture in this part of the season, whether we were coming in to the fixture unbeaten in the Magners League or if in the position we are now in. It is a huge, high pressure game and the players have been looking forward to it for a long time.
"Gloucester got their season off to a flying start playing some great rugby and chalking up some high scores in the Premiership. They have recruited well over the last few seasons and are a strong side and will certainly provide a stern test for us on Friday night."
ULSTER (v Gloucester): Bryn Cunningham; Tommy Bowe, Andrew Trimble, Rob Dewey, Mark McCrea; Paddy Wallace, Isaac Boss; Justin Fitzpatrick, Rory Best (capt), Bryan Young, Justin Harrison, Carlo Del Fava, Matt McCullough, Neil Best, Roger Wilson.
Replacements: Nigel Brady, Declan Fitzpatrick, Ryan Caldwell, Kieron Dawson, Kieran Campbell, David Humphreys, Mark Bartholomeusz.