Ulster put faith in Trimble for Dragons tie
He replaces Paul Steinmetz, who is sidelined for four weeks with a broken jaw, while former international James Topping is recalled to the left wing.
For their part, the Dragons’ request to have Lion Michael Owen available has been denied. But fly-half Craig Warlow returns after a stomach bug, while locks Ian Gough (eye) and Luke Charteris (calf) have recovered from their knocks to start.