Foley has joined the call for calm heads and realistic expectations among Irish fans buoyed by two successive wins at the start of the RBS 6 Nations Championship this year.
He echoed his coach Eddie O'Sullivan's contention that the French are still a class act despite their opening-day Twickenham defeat to England.
"It's going to be a very tight game," said the Munster star.
"They're a very good side and you just have to take a look at their pack - they're awesome up front and for us it's going to be a long day at the office if we don't front up early on in the match.
"We have to command our set-pieces and try and control the pace of the game and the possession we get.
"We can't afford to take a backward step all day and we can't afford the lapses in concentration and commit the errors we had against Italy in Rome.
"We have to be ruthless on Saturday. It's going to be very close, a score in it I reckon, but I think we'll just nick it.
"Our feet are firmly planted on the ground. We're just concentrating on this game on Saturday and the obstacles it poses to us as a team.
"We do see a lot of danger in front of us but it's just a matter of trusting in our own ability and trying to produce our best possible performance on the day."