Connacht top the Pool 2 table after a stunning victory in Montpellier and Ruddock admits they are now the 'side to beat' if his team have any hope of last eight qualification.
Only the five Pool winners will qualify for the quarter-finals, where they will be joined by three Heineken Cup group runners-up.
And Ruddock knows his team must produce at Sixways when they meet in what organisers have revealed will be the 1,000th European Challenge Cup match ever to take place.
He said: "We're looking forward to getting back into the Amlin Challenge cup. It is a tough competition and we have it a little bit more hard work for ourselves by losing to Montpellier.
"It is going to tougher than it should have been at this stage and Connacht are the form team and the side to beat.
"They went to Montpellier and won, they will be coming here targeting this competition and looking to build on an excellent victory in France.
"I will pick a strong panel, a very determined team and one I will put pressure on to keep some momentum. Hopefully we will meet that challenge, get a victory and a try or two.
Warriors face Connacht twice in the space of seven days, with a trip to Galway next Friday (December 18).
And Ruddock has revealed he will have to keep one eye on the massive Boxing Day clash with Northampton Saints as he selects his side.
"We will certainly know each other inside out after these two games, but we have also got a very tough Guinness Premiership fixture just around the corner against Northampton," he said.
"We will see what happens on Saturday, but there is a chance I will rotate my squad when we go out to Connacht and freshen a few guys up for the Northampton game.
"We want to give a good account of ourselves, particularly at home in the Guinness Premiership. We are building momentum in terms of our performances and we have just got to transfer that into results.
"We have got to be at the top of our game to beat Northampton so I am going to have to balance up our ambition in this tournament with some useful selections to keep people fresh."
