The 25-year-old Clermont Auvergne outside-half was withdrawn at half-time in France’s 29-0 win over Italy in the RBS 6 Nations last Sunday.
Lopez, who made his debut against New Zealand in June 2013, had started seven consecutive matches since starting at outside-half against Fiji last November, but has now been ruled out for between four and six weeks.
While Les Bleus have not revealed the nature of his injury, Lopez is understood to be out with a knee problem.
Head coach Philippe Saint-André has called up Racing Métro scrum-half Maxime Machenaud, but Stade Français outside-half Jules Plisson is likely to take the 10 jersey with Machenaud, who has 18 caps, a contender for a place on the bench with Castres scrum-half Rory Kockott.
France had already been hit by the loss of outside-half Pierre Bernard, who had been in the squad prior to the Wales defeat in Paris, but suffered a knee injury on club duty for Bordeaux-Bègles and was replaced by Plisson.
France still have a mathematical chance of winning the championship if they can produce a big win over England and Wales and Ireland both lose earlier on “Super Saturday”.
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