Toulouse opened with a two-point win over London Wasps and Heineken Man of the Match Johnston said: “I haven’t had a look at the Dragons yet. I know they lost to Glasgow but we have to take this competition week by week as this tournament can change with the flick of a switch.
“But we will definitely work hard this week as we know the Dragons are tough to beat at home. It’s definitely a big challenge for us.
“The pressure is always greater on us because we are the defending champions. A lot of teams play their best games against us and the Dragons will be no different to that.
“It’s important that we pull through and defend our title. We want to be one of the best teams in Europe but it’s hard to keep doing it every year.
“We will try to win this trophy again. A lot of people say our Pool is easier than the others but just look at the game against Wasps. Anyone can be turned over on any given day.
“We knew we had to front up and fortunately we got on the front foot. We are pretty happy with the result and the win.
“We always knew Wasps would be pretty tough and they gave us a good match for the full 80 minutes.
“Today was our day. Heineken Cup matches are always won up front. It was important we fronted up.
“The memories of Wales in the last few years won’t affect us. We will look at Newport and play from there. We don’t look at the past.”