Centre is the other major problem area, ex-Gloucester man Matthew Watkins out for three weeks with a side strain, Pat Leach and Adam Hughes also out.
Ashley Smith, Gavin Thomas, Jason Tovey and Rob Sidoli should be fit to return.
"If we can combine the attitude we showed [in the 23-10 Magners League win over Connacht] with better finishing and skills, we can go to Gloucester with confidence," said the Dragons' stand-in skipper Luke Charteris.
"I don't think it's a step up in class. We've got a lot of respect for the Guinness Premiership and the players in it.
"But you go to Munster, Leinster [in the Magners League]… they're all just as physical."
"The boys will have to step it up but not necessarily because it's a Premiership team."
Gloucester and the Dragons' pool two rivals Glasgow Warriors and Biarritz Olympique face off in Scotland on Saturday.
And in-form back-rower Joe Bearman says the Dragons can get off to a solid start ahead of the challenges to come.
"We played at [Gloucester] last year and lost by a couple of points, so we go there with more confidence this year," he told BBC Sport Wales.
"Our scrum has been under a bit of pressure with props coming in after a couple of injuries. We can only get better in that area and we will work on that."