Wales have prided themselves on their defence this tournament, but five tries conceded in five matches does not impress France who, even in defeat to the All Blacks, scored two and should have had at least two more.

The France defence coach, Dave Ellis, believes Wales have yet to be examined by a resourceful attack in the World Cup, and rated Shaun Edwards, his counterpart this weekend, as the rival he has most respect for.

"They have played South Africa and Ireland, two teams who do not score a lot of tries," said Ellis. "Wales have so far met sides who kick and are defence-oriented, so logically they have not been tested much. That will change on Saturday, no doubt.

"Wales tackled low against Ireland, but we have been doing that for 12 years. Wales's line-speed has become quicker and they have some exceptional back-rows, like Sam Warburton, who are superb over the top of the ball. He is winning lots of turnovers, along with his back-row colleagues."

One Wales player no defence has yet managed to combat is the 17st centre Jamie Roberts, who has won collision after collision in the past six weeks and who ran into Donncha O'Callaghan so hard in the opening minute of last weekend's quarter-final that the Ireland second-row found himself on the ground shaking his head.

"The problems other defences have had with Roberts do not concern me," said Ellis. "We have played against him on numerous occasions and he is a threat. We have to stop him doing what he has managed so far. I have been quite impressed with Rhys Priestland [the Wales outside-half] since he played against South Africa. He has fitted in perfectly with what Wales want to do. He is serving players early and getting the ball wide, causing teams major problems.

"He is standing back and operating. Before, on occasions, Wales had Stephen Jones getting a bit too close to the line, allowing defences to get to him. I do not think it would alter the way they play if Priestland had to pull out: Wales are on a roll. The ratings they have had this tournament are justified. They nearly beat South Africa and have won all their other games. They are always tough opponents. When we have won the grand slam or the Six Nations, the most difficult game has always been Wales."

Ellis said that Wales had clearly made progress this tournament, but it was little compared with the leap France had to make after their first four matches – when they struggled for periods against Japan and Canada before losing to New Zealand and Tonga– against England in last weekend's quarter-final.

"We made a hell of a lot more progress and we intend to take another few steps on Saturday. Everything that was written about the supposed differences between the players and Marc [Lièvremont, the coach] were blown out of all proportion. A couple complained they had been criticised in public, but he says it to the players before the media. I played the game for many years and I did not like being told if I had a bad game either.

"The spirit is good now and it always has been. We have lost at the semi-final stage in the last two tournaments and it is at the back of the minds of those players who were involved in both. I would imagine they had had a few words amongst themselves.

"Wales have a number of young players and that may cause them problems as the game approaches. We have to make sure we put them under pressure but with their dangerous back three, if we kick the ball at the wrong time and the wrong place, we will be punished."

Wales are likely to use the burly Roberts to run at Morgan Parra, the scrum-half who has started at outside-half in the last three matches and who was exposed in defence by New Zealand and Tonga.

"I do not think it was Morgan's fault against the All Blacks," said Ellis. "The people around him were overcompensating. In one of the tries we conceded, Thierry Dusautoir was more concerned about who Morgan was going to tackle than who he was supposed to tackle. That is what caused the problem. Morgan is one of the most intelligent players I have worked with, really tuned in."

Ellis said he was relishing his battle with Edwards. "We see each other occasionally when I am in England, although not socially. Shaun is the defence coach I have most respect for in the world. He is outstanding and he is about more than defence. He is the head coach at Wasps and perhaps he has a future in that capacity at international level as well."