LONDON (AP) — Chelsea forward Christopher Nkunku had knee surgery and will be sidelined for “an extended period,” the Premier League club said Tuesday.

The 25-year-old France international joined Chelsea this summer from Leipzig for a reported transfer fee of $66 million.

Nkunku sustained the injury during Chelsea’s preseason match against Borussia Dortmund in Chicago.

Chelsea, which spent heavily last season with disappointing results, issued a brief statement that Nkunku had undergone an operation “and will now begin a rehabilitation program with the club’s medical department.”

Nkunku has made 10 appearances for France and played for Paris Saint-Germain before joining Leipzig in 2019.

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