Chelsea have confirmed that Christopher Nkunku has undergone surgery on a knee injury which will rule him out for a significant period.

Nkunku, a £52m signing from RB Leipzig this summer, went down during a pre-season friendly against Borussia Dortmund and initial optimism over his injury soon turned to despair when it became apparent surgery was required.

The 25-year-old has now gone under the knife, with Chelsea writing in a statement: "Nkunku has sustained a knee injury which will rule the forward out for an extended period.

"The 25-year-old has undergone an operation and will now begin a rehabilitation programme with the club’s medical department."

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The news comes as an enormous blow for Chelsea as Nkunku had impressed during pre-season, forming an impressive partnership with fellow new signing Nicolas Jackson as the duo inspired an unbeaten summer for the first time in over ten years.

Having played as both a striker and an attacking midfielder, Nkunku's versatility will be a real miss for Mauricio Pochettino, who has given the likes of Ian Maatsen and Carney Chukwuemeka plenty of opportunities to prove themselves in attacking positions in pre-season.

Pochettino has admitted to being open-minded when it comes to Chelsea's pursuit of a new striker, with Dusan Vlahovic of Juventus currently under consideration as the Blues seek to finally part ways with Romelu Lukaku.

Juventus are happy to swap the two strikers but 90min understands their demand that Chelsea pay an additional €40m (£34.5m) has proven problematic in negotiations.

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This article was originally published on 90min as Christopher Nkunku undergoes surgery on pre-season knee injury.