The 30-year-old sustained a muscle injury in training on 7 January and an MRI scan has confirmed that he is experiencing a recurrence of the hamstring trouble that saw him miss three weeks of action in November.
The former Arsenal FC player sat out Saturday's 2-0 French Cup win at ES Viry-Châtillon, and depending on the results of further tests, could be sidelined until the start of February. He is certain to skip Lyon's trip to FC Sochaux-Montbéliard tomorrow for their first Ligue 1 game of 2005.
While Lyon have no European engagements until their UEFA Champions League Round of 16 tie at Werder Bremen on 23 February, January will be a tough month for the still-unbeaten Ligue 1 leaders as they face five league matches. They are aiming to win a fourth consecutive title.
French international Wiltord, who joined Lyon last summer, has been a major factor in Paul Le Guen's side's success this term, scoring one goal in 12 league outings and one in four Champions League appearances.
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