New Chelsea signing Christopher Nkunku could face months out after scans revealed the injury he suffered in a pre-season friendly last week is worse than first feared.

In a major blow to Chelsea ahead of the new season, Nkunku has sustained a meniscus injury and undergone a knee operation.

The £52million summer signing from RB Leipzig injured his knee in a heavy collision with Borussia Dortmund defender Mats Hummels in Chicago.

Chelsea head coach Mauricio Pochettino refused to blame the state of the dreadful pitch at Soldier Field, which had hosted an Ed Sheeran concert a few days before.

Nkunku has impressed during pre-season and his injury has rocked Chelsea’s plans for the new season.

He has scored three goals in five pre-season appearances playing up front, on the wing and as a No10. Chelsea lost much of their attacking identity after he went off against Dortmund and Pochettino had hoped he would make a swift recovery. But Nkunku will now miss the start of the new season.

Pochettino said last week that the injury was “bad luck”.

The Argentine, whose side kick off the season at home to Liverpool on Sunday, said: "It is not about complaining. Always we take some risks because the pitch is not perfect and that is sometimes the risk of the tour, yes.

"It was a bit unlucky in the situation but we cannot complain about the pitch and blame the pitch for why he suffered the injury. For me it was bad luck."