Chelsea forward Christopher Nkunku has undergone knee surgery that will rule the French international out for an "extended period" the Premier League club said on Tuesday.

Nkunku had already agreed a pre-contract with the Premier League club in December and has now rubber-stamped his move to Stamford Bridge.

Holders RB Leipzig and five-time winners Eintracht Frankfurt have emerged from the shadows of Bayern Munich and Borussia Dortmund to become two of Germany's most successful sides in recent seasons.

Eintracht Frankfurt striker Randal Kolo Muani will replace RB Leipzig's Christopher Nkunku in the France squad for the World Cup in Qatar, the French federation (FFF) said on Wednesday.

France forward Christopher Nkunku will miss the World Cup after suffering an injury in training on Tuesday, the French federation (FFF) said.