Warriors edged to victory at the Arcul de Triumf stadium in the same competition last term in a fixture that was dominated by atrocious conditions after heavy rain and ice cold conditions descended.
Ruddock has now told his troops they will face an equally difficult task on Sunday against a quickly improving Bucuresti Oaks outfit.
"I was really pleased with the professional performance by us against Petrarca Rugby," said Ruddock. "But it will be much tougher against Bucuresti Oaks, they will be more physical, better organised and a tougher test all round.
"We got a victory there last season in bad weather conditions, but they have strengthened with a Kiwi players and I have been in touch with their team manager. They had a pre-season tour to New Zealand and Fiji and they have had a month together so they have had good preparation for this competition.
"They ran Bourgoin close, a French team with a big reputation, so that is a very good effort by the Romanians. It shows we will have to be professional.
"We have switched this game and brought it forward and the weather forecast is much better. Hopefully that will allow us to play some good rugby and get the ball wide to get outside the physical contest that I'm sure they would thrive on."
Ruddock is keeping his team selection under wraps until Friday but has revealed that full back star Chris Latham, who notched a hat-trick last weekend, is set to be rested.
"One player we will look to rest is Latham. He has picked up a few knocks during his start to the club. He has a bruised left hand so we will probably get him rested up a ready for the Ospreys next week," added Ruddock.
"There are always injuries that impact on who we can pick, but overall we have a strong panel for this game. Matt Mullan will come back in after we rested him last week and Miles Benjamin will come back into the fold after he was ruled out with illness last week."