Castaignede eager to get back into misfiring French line-up
The Saracens star was forced to miss Les Bleus' opening two encounters after aggravating a thigh injury, but is one of three changes from the side which almost blew a 43-3 lead against Ireland a fortnight ago before hanging on for a 43-31 win.
That followed a shock 20-16 opening weekend defeat to Scotland, which blew the pre-tournament favourites' chances of the Grand Slam.