Chelsea new signing Christopher Nkuku will face a lengthy spell on the sidelines with an injury to his knee.

In a statement released by the club, Nkuku will now begin a rehabilitation programme with the club’s medical department after undergoing knee surgery.

Nkuku was substituted in the 22nd minute of Chelsea’s final preseason fixture against Borussia Dortmund after a collision with Dortmund defender Mats Hummels.

The 25-year-old joined Chelsea in the summer for £52 million from German Bundesliga side RB Leipzig.

He scored three goals in five preseason games for the club.