France cannot afford to let Ireland take the initiative next Sunday because there will be no way back unlike against the Scots and French dreams of an RBS 6 Nations Grand Slam will lie in tatters said coach Philippe Saint-Andre.

The 44-year-old former France captain - who replaced the unpredictable Marc Lievremont after the 8-7 World Cup final defeat by the All Blacks last October - admitted his upbeat assessment immediately after beating Scotland 23-17 on Sunday had been replaced by a dose of realism after watching the video of the game.

The former wing - capped 69 times from 1990-97 - views the Irish match as a step up in terms of a challenge after two wins against Italy (30-12) and then coming from 10-0 down to beat the gutsy Scots.

The Irish - who last won in Paris in 2000 - arguably come into the match in better spirits than they would have been in when it was originally scheduled earlier this month but was called off at the last minute because of a frozen pitch.

However having been beaten 23-21 in their opener by Wales they boosted their morale with a convincing enough 42-10 win over Italy on Saturday and Saint-Andre is eager his side don't allow the Irish to build on that in the early stages in Paris.

"After a match when you win, you accentuate the positive," said Saint-Andre.

"However, after you watch the video and you resume preparing for the next game, you see how imperative it is to improve on the things that didn't function.

"In the Scottish game we were too tame at the beginning, we lost too many balls in the rucks, especially in the first half-hour, and missed too many tackles. These are the main areas we will work on this week.

"What we really need to change is that we have to hit the ground running from the kick-off and not sleepwalk through the opening 20 minutes like we did against Italy and Scotland.

"If we do that against the Irish, it will not go well for us at the Stade de France."

Saint-Andre, who has based the principles he wants from his players such as determination and dedication on his grandfather who was along with 15 others executed by the Germans in 1944, said he had also liked a lot of what he saw in an entertaining match.

"Of course as a coach when you wake up and you have won everything is a lot better," said Saint-Andre, who cut his coaching teeth in England with Gloucester.

"Afterwards we know that we have played two games and we know that we still have to move up to a very high level of play against teams of a much better calibre than Scotland or Italy.

"We are of course happy to win, happy to have been able to come back from 10-0 down, and happy with the scrum which was a major positive.

"But we still have many things to improve. I repeat that defensively we missed too many tackles and at international level that is unforgiveable."

Saint-Andre, who has also had spells coaching Bourgoin, English side Sale and Toulon, admitted that too much was being asked of the French players in staying fit and on their best form because of the amount of rugby they played in comparison to other countries.

"Yes I am concerned because I don't think that the players can play 40 matches like they are doing this year, it is impossible," he said.

"When one sees the required intensity in order to play at this level when the ball is in play like it was against Scotland for 40-50 minutes ... then it is vital to have a huge swathe of time to prepare, periods where they can recuperate and not play and then competition time.

"This is really sport of a very, very high level.

"It is also for this reason that so many people come to watch the matches. I think it is a superb spectacle, when the ball is in play permanently.

"For that, one has to have a huge group of players to draw on, one has to have athletes. We have them but we have to unearth some more."