Shaun Edwards warned France will be in for a "hiding" against Ireland in the Six Nations next weekend if they fail to raise their game after clinging on to beat Italy 29-24.
The defending champions needed a Matthieu Jalibert try with 14 minutes to play at Stadio Olimpico on Sunday to start the defence of their title with a bonus-point win.
First-half tries from Thibaud Flament, Thomas Ramos and debutant Ethan Dumortier put the holders well on course for victory, but an Ange Capuozzo score and three Tommaso Allan penalties meant they only led 19-14 at the break.
A penalty try that also resulted in Charles Ollivon being sent to the sin-bin and another three points for Allan sensationally put the resurgent Azzurri in front with just under 20 minutes to play.
France were able to extend their winning run to 14 matches courtesy of Jalibert's finish, but they had to withstand late pressure and Allan missed a kick at goal as Italy fell just short of claiming a famous victory.
Les Bleus face Ireland, the world's top-ranked side, at the Aviva Stadium next Saturday and defence coach Edwards says their winning streak will come to a juddering halt if they fail to improve on their display in Rome.
He told ITV Sport: "First half, we were quite dominant. They came on leaps and bounds in the second half and obviously at the end it was a very tight affair, but we are in a good habit of winning tight games at the moment.
"It happened against Australia, against South Africa, it's happened in a few games.
"Hopefully we can continue that habit, but I think we all know if we don't put up a better performance next week we'll be on the end of a 15-30 point hiding."
Indisciplined France conceded 18 penalties, although Edwards suggested the count should not have been so high.
"Certainly against the defence it's something I will be looking at this week and I'll be honest, I've been in the game for 20 years and that's the most penalties I've ever had against the defence.
"It's something we pride ourselves on with the French team in particular and all the way through with Wales, Wasps, etc. We'll have to go through it in detail with the referees, because it's the first time my defence has been penalised so much."