Renato Sanches (centre) appeared in Lille's season Ligue 1 opener at Metz
Lille's Portugal midfielder Renato Sanches has undergone surgery on a knee injury and will be out for six weeks, the French champions announced.
Sanches had been struggling with his knee for several weeks.
He played the entire 3-3 draw at Metz in the first round but was not in the squad for Saturday's 4-0 home loss to Nice.
Lille said in a statement on Monday evening that he would begin rehabilitation this week.
Sanches appeared in 23 games as Lille won Ligue 1 last season.
A six-week absence would means he misses the club's first two Champions League group-stage matches in September.
The injury also reduces the chances that Lille will sell one of their most valuable assets before the transfer window closes at the end of August.
Sanches had been linked to several clubs, including Liverpool and Barcelona, and the expected fee of around 35 million euros (41.2m dollars) would have solved some of the club's financial problems.
Lille had already sold central midfielder Boubakary Soumare, who played 32 times in Ligue 1 last season, to Leicester for a fee reported to be around 20 million euros.
Sanches, who was part of Portugal's Euro-winning team in 2016, appeared in all his country's four games in this summer's finals.
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