France flanker Charles Ollivon said Tuesday that England's win over Ireland at the weekend had made "a very strong impression", five days before the teams meet in Lyon in the final round of matches in this year's Six Nations.
The English, who had been beaten by Scotland in the previous round, produced their best performance since coming third in last year's World Cup as they took down the Grand Slam favourites with a thrilling 23-22 victory at Twickenham.
France, meanwhile, bounced back from some unimpressive performances in the opening three rounds with a 45-24 win over Wales in Cardiff.
"We're expecting a big defence," former captain Ollivon told a press conference at France's training base just outside Paris.
"We've seen how they (England) have changed things. They're much more aggressive, they have a much stronger, much quicker line-out.
"They put a lot more pressure on their opponents than they used to.
"When it comes to contact too, they're very strong. I saw the match against the Irish and to move them around like that in one-on-one situations, you have to be really solid.
"They made a very strong impression on me."
The English, who are getting used to life without their long-serving captain Owen Farrell who has taken time away from the international game, refused to buckle when they conceded a late James Lowe try and with it the lead.
Instead they went up the other end and denied Ireland a second successive Grand Slam thanks to a last-minute drop goal from replacement fly-half Marcus Smith.
"The England team is tougher," said France's performance director Nicolas Jeanjean.
"We saw that they were very effective, with quite a lot of rush defence. There will be a lot more contact than against Wales.
"Our challenge is going to be to rise to this contest against the English."
France, who are playing their home games away from Paris because of the Olympics in the summer, opened the tournament with a 38-17 defeat by Ireland in Marseille, following that with a controversial and narrow 20-16 win in Edinburgh and a lucky 13-13 draw at home to Italy.