This is the second successive tournament that Worcester and Bucuresti have been drawn in the same group, the Warriors doing the double in 2007/08, but Ruddock is only concerned with the next meeting
"This weekend's game is going to be very, very physical," said the 2005 Wales Grand Slam winning coach.
"We know that Bucuresti are a strong side. Our away match against them back in October was very tough and we are aware of the threat they pose.
"They are very physically committed and have some great coaching with former New Zealand prop Steve McDowell, who won 46 caps for the All Blacks.
"They were most certainly very fired up for our game back in October and, having only just lost to Bourgoin the previous week, they were a tough side to beat.
"Their wing Jeff Makapelu was outstanding and scored two brilliant tries. He's a real handful to keep in check and we are expecting another strong performance from him this weekend.
"We were lucky with the weather over in Romania, which helped us play some good running rugby, but a wet day will give them the opportunity to slow down the game and play to their strengths so the conditions could be crucial.
"Their pack is very solid and physical - everything you'd expect from a set of Romanian forwards - and we played some of our best rugby to beat them. We are going to be looking at the contact area, where they gave us some problems last time, and concentrate on our ball retention."
Worcester, playing in Europe for only their fifth season, may have their work cut out in attempting to earn home quarter-final advantage, even with back-to-back home games against Bucuresti Oaks and then Petrarca Rugby in the final round of matches.
"Our postponed games against Sale Sharks and then Harlequins means we have not had a match since 27 December - and that could be either a good or a bad thing," added Ruddock.
"On the plus side we have avoided any injuries but on the down side it means we could be short of match practice, and that could count against us on the day.
"But it's an extremely long season with a lot of high speed contact and when you're coming up against a side as physical as Bucuresti, any extra recovery time beforehand will help.
"We've got a good run in for the last two rounds of the Pool stages with home matches against Bucuresti and Petrarca and sitting at the top of Pool 3 we are obviously looking to get maximum points.
"If we can do then hopefully we could get a home quarter-final, but, with several teams doing very well this season, it's out of our hands whether we get that last eight home game or not."