CHELSEA’s new £52million signing Christopher Nkunku has undergone knee surgery and will be out for months.

It is a huge blow to the Blues ahead of their Premier League opener this weekend.

Christopher Nkunku has undergone knee injuryCredit: Getty

The Frenchman was forced off in last week’s friendly against Borussia Dortmund after damaging his left meniscus.

Chelsea had initially hoped he would only be out for weeks instead of months.

However, the forward will now be out for at least four months after having surgery on the injury.

As a result, Nkunku is now unlikely to play until December in a huge blow for Mauricio Pochettino.

In a club statement, Chelsea confirmed: “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.”

Nkunku is a new arrival at Stamford Bridge, with his move to the club from RB Leipzig finalised earlier this summer.

The condition of the pitch in Chicago had been pinpointed as a potential reason for the injury.

Soldier Field had recently hosted an Ed Sheeran concert prior to the match between Chelsea and Dortmund.

Speaking after the match, Pochettino told reporters: “I didn’t see the action but it is not about complaining.

“Always we take some risks because the pitch is not perfect because they are using it for different sports and that is sometimes the risk of the tour, yes.

“But I think it was a bit unlucky in the situation but we cannot complain about the pitch and to blame the pitch for why he suffered the injury. For me it was bad luck.”

Chelsea begin their campaign at home to Liverpool on Sunday.

New signing Nicolas Jackson is expected to lead the line in Nkunku’s absence, having arrived from Villarreal for £32million this summer.