But Ospreys flanker Thomas insists Wales will meet fire with fire up front in the historic showdown at the Millennium Stadium.
Thomas, 27, said: "France are the form team in the championship but we won't fear them. "We will respect them but it has been instilled into the squad that we put in the graft and hard work - we pride ourselves on working harder than the opposition.
"We like to train and play at a high intensity and the lungs are always burning by the second half. We will make sure they are in for a tough game."
Wales have been decimated among the forwards with first-choice quartet Gethin Jenkins, Matthew Rees, Alun Wyn Jones and Andy Powell ruled out through injury or suspension.
But experienced Thomas, who will switch from lock to the back-row following the dramatic last-gasp win over Scotland, believes Wales' stand-ins will prove their worth.
The 52-cap star added: "We have strength in depth and Bradley Davies and Deiniol Jones have played well together in the big European matches for the Blues.
"They don't get the praise they should and do a lot of the unseen work. You need players like that in any good side.
"Huw Bennett was a Grand Slam winner in 2008 so the changes should not affect us. France will provide a great test for us but we believe we can match them up front."
Hooker Bennett will form an all Ospreys front-row trio alongside Paul James and Lions tight-head prop Adam Jones.
Jones said: "We've played together for the region for the last seven years and that will give us confidence. We will back ourselves.
"We know exactly what to expect from the French forwards but we will try and get in their faces.
"I believe we have one of the most under-rated players in Europe in Paul and Friday night will be a chance for him to show how good he is."