The 25-year-old damaged the anterior cruciate ligament in Lyon's 3-0 win over Toulouse, which included a brace for goal machine Karim Benzema.

"Francois Clerc had a MRI scan this morning which revealed the seriousness of his injury… He will be out between five and six months," a statement on the French club's web site stated.

Clerc is currently first-choice right-back for France coach Raymond Domenech, following the retirement of Willy Sagnol.

The versatile defender was part of Les Bleus squad in the disappointing EURO 2008 campaign, which saw them eliminated from the first round.